Perinatal outcomes following fetoscopic laser surgery for early twin-to-twin transfusion syndrome: Systematic review and meta-analysis

INTRODUCTION

Our objective was to investigate outcomes in twin-to-twin transfusion syndrome (TTTS) treated with fetoscopic laser surgery (FLS) at <18 weeks vs ≥18 weeks, and to conduct subgroup analysis of TTTS with FLS at <16 weeks vs 16-18 weeks.

MATERIAL AND METHODS

PubMed, Scopus and Web of Science were searched systematically from inception until May 2023. Primary outcome was survival, and secondary outcomes included preterm premature rupture of membranes (PPROM), preterm birth and gestational age (GA) at delivery.

RESULTS

Nine studies encompassing 1691 TTTS pregnancies were included. TTTS stage III was significantly more common in TTTS pregnancies treated with FLS at <18 weeks (odds ratio [OR] 2.84, 95% confidence interval [CI] 1.24-6.54), and procedure duration was shorter at <18 weeks (MD -5.27 minutes, 95% CI -9.19 to -1.34). GA at delivery was significantly earlier in TTTS pregnancies treated with FLS at <18 weeks (MD -3.12 weeks, 95% CI -6.11 to -0.13). There were no significant differences in outcomes, including PPROM, PPROM at <7 days post-FLS, preterm birth at <28 and <32 weeks, delivery at <7 days post-FLS, and survival outcomes, including fetal demise, live birth and neonatal survival. Similarly, TTTS stage III was more common in TTTS with FLS at <16 weeks than at 16-18 weeks (OR 2.95, 95% CI 1.62-5.35), with no significant differences in the aforementioned outcomes.

CONCLUSIONS

In early TTTS treated with FLS, outcomes were comparable between those treated at <18 weeks compared with ≥18 weeks except for GA at delivery, which was 3 weeks earlier. In the subset treated at <16 weeks vs 16-18 weeks, the procedure was feasible without an increased risk of very early preterm birth or perinatal mortality.

Risk of intrapartum cesarean delivery in twin pregnancies: A retrospective cohort study

OBJECTIVE

To compare the risk of intrapartum cesarean delivery (CD) between patients with twin and singleton pregnancies undergoing a trial of labor and identify risk factors for intrapartum CD in twin pregnancies.

METHODS

The present study was a retrospective cohort study of patients with a twin or singleton pregnancy who underwent a trial of labor at ≥340/7 weeks in a single center (2015-2022). The primary outcome was the rate of intrapartum CD. In twin pregnancies, this outcome was limited to CD of both twins. The association of plurality with intrapartum CD was estimated using multivariable Poisson regression.

RESULTS

A total of 20 754 patients met the study criteria, 669 of whom had a twin pregnancy. Patients with twins had a greater risk of intrapartum CD (of both twins) than those with singleton pregnancies (22.1% vs 15.9%, respectively; aRR 1.38 [95% CI: 1.15-1.66]), primarily due to a greater risk of failure to progress. In addition, 4.1% of the twin pregnancies had a CD for the second twin, resulting in an overall CD rate in twin pregnancies of 26.2%. Variables associated with intrapartum CD in twin pregnancies included nulliparity (aOR 3.50, 95% CI: 2.34-5.25), birthweight discordance >20% (aOR 2.47, 95% CI: 1.27-4.78), and labor induction (aOR 1.64, 95% CI: 1.07-2.53). The rate of intrapartum CD was highest when all three risk factors were present (67% [95% CI: 41%-87%]).

CONCLUSION

Twin pregnancies are associated with a greater risk of intrapartum CD than singleton pregnancies. Information on the individualized risk of intrapartum CD may be valuable when counseling patients with twins regarding mode of delivery.

Association of fetal growth restriction and stillbirth in twin compared with singleton pregnancies

OBJECTIVE

Twin pregnancies are at an increased risk of stillbirth compared to singletons. Fetal growth restriction (FGR) is a leading cause of perinatal mortality and morbidity, in both singleton and multiple pregnancies. Whether the contribution of FGR to stillbirth in twin pregnancies differs from that in singletons is yet to be determined. The main aim of this study was to determine the association between FGR and stillbirth in twin compared to singleton pregnancies. The secondary objectives include an assessment of the contribution of FGR to stillbirths, stratified by gestational age at delivery. Furthermore, we aimed to compare the association between FGR and stillbirth in twin pregnancies using the twin-specific versus singleton birthweight charts, stratified by chorionicity.

METHODS

This was a cross-sectional study including pregnancies receiving obstetric care and birth at St George's Hospital, London. The exclusion criteria included triplet and higher order pregnancies, those resulting in miscarriage or livebirths at or prior to 23+6 weeks, or had a termination of pregnancy, or with missing data on the gestational age at birth. FGR and small for gestational age (SGA) were defined as birthweight <5th and <10th centile, respectively. While standard logistic regression was used for singleton pregnancies, the association of FGR and SGA designation with stillbirth in twin pregnancies was investigated with mixed-effects logistic regression models. For twin pregnancies, intercepts were allowed to vary for twin pairs to account for inter-twin dependency. Analyses were stratified by gestational age at delivery and chorionicity.

RESULTS

The study included 95,342 singleton and 3,576 twin pregnancies. There were 494 (0.52%) stillbirths in singleton and 41 (1.15%) stillbirths in twin pregnancies (17 dichorionic and 24 monochorionic). FGR and SGA were significantly associated with stillbirth in singleton pregnancies, across all gestational ages at delivery (before 32 weeks- SGA: OR 2.36; 95% CI 1.78-3.13, p<0.001 and FGR: OR 2.67; 95% CI 2.02- 3.55, p<0.001; between 32-36 weeks- SGA: OR 2.70; 95% CI 1.71-4.31, p<0.001 and FGR: OR 2.82; 95% CI 1.78- 4.47, p<0.001; above 36 weeks- SGA: OR 3.85; 95% CI 2.83 - 5.21, p<0.001 and FGR: OR 4.43; 95% CI 3.16 - 6.12, p<0.001) A greater proportion of fetuses from twin pregnancies were diagnosed as SGA and FGR when singleton compared to the twin-specific chart was used (48.43% vs. 9.12%, and 36.73% vs. 6.23%, respectively). When stratified by gestational age at delivery, both SGA and FGR determined by the twin-specific charts were associated with significantly increased odds of having a stillbirth for those delivered before 32 weeks (SGA: OR 3.87; 95% CI 1.56-9.50, p=0.003 and FGR: OR 5.26; 95% CI 2.11-13.01, p<0.001), those delivered between 32-36 weeks (SGA: OR 6.67; 95% CI 2.11-20.41, p=0.001 and FGR: OR 9.54; 95% CI 3.01-29.40, p<0.001) and those delivered beyond 36 weeks (SGA: OR 12.68 95% CI 2.47-58,15, p=0.001 and FGR: OR 23.84; 95% CI 4.62-110.25, p<0.001), whereas the association of stillbirth with either SGA or FGR was inconsistent when analysed using singleton charts (before 32 weeks- SGA: p=0.014 and FGR: p=0.005; between 32-36 weeks- SGA: p=0.036 and FGR: p=0.008; above 36 weeks- SGA: p=0.080 and FGR: p=0.063). For dichorionic twins delivered before 32 weeks, the odds of an SGA or FGR fetus having a stillbirth was increased when analysed using twin-specific charts. In contrast, monochorionic twins delivered before 32 weeks showed lower and non-significant associations with stillbirth for both SGA and FGR cases using either twin-specific or singleton charts. In dichorionic twin pregnancies delivered between 32-36 weeks, the OR for stillbirth of SGA using twin birthweight chart was 6.70 (95% CI 0.80-56.46, p=0.059), and using singleton chart was 0.92 (95% CI 0.11-7.71, p=0.934) and statistically non-significant. Similarly, the OR for stillbirth of FGR using twin birthweight chart and singleton chart was 9.59 (95% CI 1.14-81.06, p=0.025), and 1.40 (95% CI 0.17-11.76, p=0.735), respectively. On the other hand, in monochorionic twin pregnancies delivered between 32-36 weeks, the OR for stillbirth of SGA and FGR using twin birthweight chart was 9.37 (95% CI 2.20- 37.72, p=0.001), and 13.55 (95% CI 3.12 - 55.94 p < 0.001) respectively.

CONCLUSIONS

Our study demonstrates a significant association between SGA, particularly for FGR, with increased odds of stillbirths in singleton pregnancies across all gestational ages. For twin pregnancies, when twin-specific charts were used, SGA and in particular FGR were associated with a significantly increased risk of stillbirth, across all gestational ages at delivery. This article is protected by copyright. All rights reserved.

Second twin outcome at birth: retrospective analysis in a single tertiary centre in Malaysia

OBJECTIVES

To investigate factors associated with outcome of second twin during labour.

METHODS

The study was a retrospective cohort study in a single tertiary centre in Malaysia from 2014 until 2018 involving all twin pregnancies delivered at or more than 24 weeks of gestation.

RESULTS

Total of 409 twin pregnancies were included. Dichorionic twin comprises of 54.5 % (n=223) and 45.5 % (n=186) are monochorionic. Women with dichorionic pregnancies are significantly older (p<0.001), have more pre-existing medical disorders (p=0.011) and fetal structural anomalies (p=0.009). Monochorionic pregnancies are significantly more amongst Malay (p=0.01) and conceived spontaneously (p<0.001). There are significantly more fetuses both in cephalic presentation (p=0.026), birthweight discrepancy more than 20 % (p=0.038) and shorter mean inter-twin delivery duration (p=0.048) in monochorionic pregnancies. Second twin delivered with Apgar score <7 is significantly more in dichorionic pregnancies (p=0.006). The second twin is associated with lower birthweight, small for gestational age and arterial cord pH<7.25. Within the group of women who delivered both fetuses vaginally, there was significantly more second twins with intertwin delivery duration less than 30 min who were delivered vaginally without instrumentation (p=0.018). There was significantly more second twin with intertwin delivery duration of 30 min and more with arterial cord pH<7.25 (p=0.045). Those who delivered spontaneously had inter-twin delivery duration within 15-29 min. The outcome of second twin is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth.

CONCLUSIONS

The neonatal outcome for the second twin at birth is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth in a cohort managed with non-active management of the second twin in Malaysia.

Gene-environment transactions between peer cigarette use, parental supervision, and Chinese adolescent cigarette smoking initiation

INTRODUCTION

The initiation and continued use of tobacco products constitute an ongoing source of preventable disease that continues to pose a significant risk to global adolescent health. Scarce research has sought to explore the influences of two well-known environmental risk factors, parental supervision and peer cigarette use, on genetic and environmental contributions to adolescent cigarette use, especially in non-Western populations.

METHODS

Following 602 Chinese twin pairs (52% female, N = 1204) from early to middle adolescence at two-time points (Mage = 12 and 15) from 2006 to 2009 and using multivariate biometric modeling, this study examined gene-environment interplay (i.e., gene-environment correlation and interaction) between perceived parental supervision, peer cigarette use, and adolescent cigarette smoking initiation.

RESULTS

From early to middle adolescence, genetic influences on cigarette smoking initiation became more pronounced, whereas shared environmental influences that promote similarity between family members diminished. Genetic factors primarily explained the links between parental supervision and cigarette smoking initiation in mid-adolescence. Peer cigarette use displayed stronger associations with and moderating potential in adolescent cigarette smoking initiation than parental supervision. High levels of peer cigarette use amplified genetic risk for cigarette smoking initiation in mid-adolescence.

CONCLUSIONS

Chinese adolescent cigarette smoking initiation involves dynamic gene-environment transactions primarily with peer processes over development. Mid-adolescence constitutes a developmental period wherein underlying genetic risk for cigarette smoking initiation is particularly sensitive to peer influences. Targeted interventions aimed at reducing Chinese adolescent cigarette smoking initiation should focus on peer processes during this developmental period.

Transvaginal cerclage for prevention of preterm birth in twin pregnancies with cervical dilatation or shortening: A prospective observational study

OBJECTIVE

To investigate the efficacy of transvaginal cerclage in twin pregnancies with cervical shortening, and to narrow the threshold cervical length for transvaginal cerclage.

METHODS

This is a prospective cohort study and 177 twin pregnancies with asymptomatic cervical dilatation or cervical length of 15 mm or less between 16+0 and 25+6 weeks of pregnancy were included. Patients independently chose either transvaginal cerclage (n = 129) or no cerclage treatment (n = 48) after being consulted on the risk and potential benefit of transvaginal cerclage. The primary outcome measures were gestational age at delivery and neonatal survival rate.

RESULTS

Compared with the no cerclage group, the cerclage group exhibited a higher gestational age at delivery (32.1 ± 4.5 vs 28.3 ± 6.2 weeks, P < 0.001) and a higher neonatal survival rate (86.4% vs 47.9%, P < 0.001). Subgroup analysis showed that in twin pregnancies with cervical dilatation or cervical length less than 10 mm, the cerclage group had significantly higher gestational age at delivery (31.3 ± 4.6 vs 23.4 ± 4.3 weeks, P < 0.001) and a higher neonatal survival rate (123 [85.4%] vs 4 [9.1%], P < 0.001) than the no cerclage group, but in twins when cervical length was 10-15 mm, the two measures were similar between the two groups.

CONCLUSION

Transvaginal cerclage may provide benefits for twins when cervical dilatation or cervical length is less than 10 mm, but its efficacy might not extend to twins when the cervical length is 10-15 mm. Further evidence is needed to confirm the efficacy of transvaginal cerclage for twin pregnancies with a short cervix.

Are Genetics the Predicting Factor for the Success of Migraine Surgery? A Report on Identical Twins

Migraine affects more than 1 billion people globally, with distinct genetic variations influencing susceptibility. Thereby, genetic variations play a key role in the probability of developing migraine. However, personalized genetic analysis-based treatment options in migraine treatments are limited. Notably, surgical deactivation of extracranial trigger has shown efficacy in the treatment of migraine patients with identifiable trigger points in specific anatomical locations in the head and neck region. We present the first case of monozygotic twin sisters, both experiencing occipital and temporal-triggered migraine headaches with identical history and characteristics and without response to conservative migraine treatments. After surgical intervention, targeting the greater and lesser occipital nerves as well as auriculotemporal nerves, both twin sisters exhibited an over 99% reduction in symptoms without postoperative complications. This case suggests a potential correlation between genetic background, irrespective of environmental factors, and the effectiveness of surgical deactivation of trigger points in migraine management.

Literary Identification of Differentially Hydroxymethylated DNA Regions for Type 2 Diabetes Mellitus: A Scoping Minireview

Type 2 diabetes mellitus (T2DM) is a public health condition where environmental and genetic factors can intersect through hydroxymethylation. It was unclear which blood DNA regions were hydroxymethylated in human T2DM development. We aimed to identify the regions from the literature as designed in the ongoing Twins Discordant for Incident T2DM Study. A scoping review was performed using Medical Subject Headings (MeSH) and keyword methods to search PubMed for studies published in English and before 1 August 2022, following our registered protocol. The keyword and MeSH methods identified 12 and 3 records separately, and the keyword-identified records included all from the MeSH. Only three case-control studies met the criteria for the full-text review, including one MeSH-identified record. Increased global levels of 5-hydroxymethylated cytosine (5hmC) in T2DM patients versus healthy controls in blood or peripheral blood mononuclear cells were consistently reported (p < 0.05 for all). Among candidate DNA regions related to the human SOCS3, SREBF1, and TXNIP genes, only the SOCS3 gene yielded higher 5hmC levels in T2DM patients with high poly-ADP-ribosylation than participants combined from those with low PARylation and healthy controls (p < 0.05). Hydroxymethylation in the SOCS3-related region of blood DNA is promising to investigate for its mediation in the influences of environment on incident T2DM.

Linking genetic foundations of sleep disturbances to personality traits: a study of mid-life twins

Risk of sleep disturbances depends on individuals' personality, and a large body of evidence indicates that individuals prone to neuroticism, impulsivity, and (low) extraversion are more likely to experience them. Origins of these associations are unclear, but common genetic background may play an important role. Participants included 405 twin pairs (mean age of 54 years; 59% female) from the National Survey of Midlife Development in the United States (MIDUS) who reported on their personality traits (broad and specific), as well as sleep disturbances (problems with falling asleep, staying asleep, waking early, and feeling unrested). Uni- and bivariate biometric decompositions evaluated contributions of genetic and environmental factors to associations between personality and poor sleep, as well as unique contributions from individual traits. Neuroticism, extraversion, conscientiousness, and aggressiveness were the strongest phenotypic predictors of poor sleep. Genetic sources of covariance were about twice as large as non-shared environmental sources, and only shared genetic background accounted for links between aggressiveness and poor sleep. Neuroticism and extraversion accounted for most of the genetic overlap between personality and sleep disturbances. The findings shed light on developmental antecedents of ties between personality and poor sleep, suggesting a larger role of common genetic background than idiosyncratic life experiences. The results also suggest that emotion-related traits play the most important role for poor sleep, compared to other personality traits, and may partially account for genetic associations with other traits.

Analysis of complete hydatidiform mole in one twin using traditional and molecular techniques

A pregnant woman with hydatidiform mole in one twin was misdiagnosed as one of the twins with embryonic arrest. She chose to terminate the pregnancy and developed distant lung metastasis. After chemotherapy, she eventually recovered. This article systematically analyzes the diagnosis and treatment of hydatidiform mole in one twin to increase the awareness and reduce misdiagnosis of the disease.

Gestational diabetes in twin pregnancies-a pathology requiring treatment or a benign physiological adaptation?

There is level-1 evidence that screening for and treating gestational diabetes in singleton pregnancies reduce maternal and neonatal morbidity. However, similar data for gestational diabetes in twin pregnancies are currently lacking. Consequently, the current approach for the diagnosis and management of gestational diabetes in twin pregnancies is based on the same diagnostic criteria and glycemic targets used in singleton pregnancies. However, twin pregnancies have unique physiological characteristics, and many of the typical gestational diabetes-related complications are less relevant for twin pregnancies. These differences raise the question of whether the greater increase in insulin resistance observed in twin pregnancies (which is often diagnosed as diet-treated gestational diabetes) should be considered physiological and potentially beneficial in which case alternative criteria should be used for the diagnosis of gestational diabetes in twin pregnancies. In this review, we summarize the most up-to-date evidence on the epidemiology, pathophysiology, and clinical consequences of gestational diabetes in twin pregnancies and review the available data on twin-specific screening and diagnostic criteria for gestational diabetes. Although twin pregnancies are associated with a higher incidence of diet-treated gestational diabetes, diet-treated gestational diabetes in twin pregnancies is less likely to be associated with adverse outcomes and accelerated fetal growth than in singleton pregnancies and may reduce the risk for intrauterine growth restriction. In addition, there is currently no evidence that treatment of diet-treated gestational diabetes in twin pregnancies improves outcomes, whereas preliminary data suggest that strict glycemic control in such cases might increase the risk for intrauterine growth restriction. Overall, these findings provide support to the hypothesis that the greater transient increase in insulin resistance observed in twin pregnancies is merely a physiological exaggeration of the normal increase in insulin resistance observed in singleton pregnancies (that is meant to support 2 fetuses) rather than a pathology that requires treatment. These data illustrate the need to develop twin-specific screening and diagnostic criteria for gestational diabetes to avoid overdiagnosis of gestational diabetes and to reduce the risks associated with overtreatment of diet-treated gestational diabetes in twin pregnancies. Although data on twin-specific screening and diagnostic criteria are presently scarce, preliminary data suggest that the optimal screening and diagnostic criteria in twin pregnancies are higher than those currently used in singleton pregnancies.

Case Report: Neonatal genital prolapse in a pair of premature Twins

Neonatal genital prolapse is a rare situation. This report presents a unique case involving a pair of premature female twins who both developed vaginal wall prolapse without any neurological deficits. Multiple factors such as selective intrauterine growth restriction, feeding intolerance, extrauterine growth retardation, and elevated intra-abdominal pressure after birth may have contributed to the development of this phenomenon. Notably, the severity of prolapse was more pronounced in the twin with lower birth weight and smaller for gestational age. After a five-month follow-up period, the twins' prolapsed vaginal wall fully retracted due to a combination of conservative treatment and enhanced nutritional support.

Risk factors associated with stillbirth and adverse perinatal outcomes in dichorionic twin pregnancies complicated by selective fetal growth restriction: a cohort study

OBJECTIVE

The main aim of this study was to investigate the perinatal outcomes of dichorionic twin pregnancies complicated by selective fetal growth restriction (sFGR).

DESIGN

Retrospective cohort study.

SETTING

Tertiary reference centre.

POPULATION

Dichorionic twin pregnancies complicated by sFGR between 2000 and 2019 in St George's University Hospital.

METHODS

Regression analyses were performed using generalised linear models and mixed-effects generalised linear models where appropriate to account for pregnancy level dependency in variables. Time to event analyses were performed with mixed-effects Cox regression models.

MAIN OUTCOME MEASURES

Stillbirth, neonatal death or neonatal unit admission with morbidity in one or both twins.

RESULTS

A total of 102 (of 2431 dichorionic twin pregnancies) pregnancies complicated by sFGR were included in the study. The Cochrane-Armitage test revealed a significant trend for increased adverse perinatal outcome rates with more severe forms of umbilical artery flow impedance, i.e. reversed, absent, positive with resistant flow and positive flow without resistance. A multivariable model including maternal and conception characteristics had poor predictive accuracy for stillbirth (area under the curve: 0.68, 95% confidence interval [CI] 0.55-0.81) and composite adverse perinatal outcomes (area under the curve: 0.58, 95% CI 0.47-0.70). When umbilical artery Doppler parameters were added to the models, the area under the curve values improved to 0.95 (95% CI 0.89-0.99) and 0.83 (95% CI 0.73-0.92) for stillbirth and composite adverse perinatal outcomes, respectively.

CONCLUSION

In dichorionic twin pregnancies complicated by sFGR, the umbilical artery Z-scores were associated with both intrauterine death and adverse perinatal outcomes.

The heritability of blood-based biomarkers related to risk of Alzheimer's disease in a population-based sample of early old-age men

INTRODUCTION

Despite their increased application, the heritability of Alzheimer's disease (AD)-related blood-based biomarkers remains unexplored.

METHODS

Plasma amyloid beta 40 (Aβ40), Aβ42, the Aβ42/40 ratio, total tau (t-tau), and neurofilament light (NfL) data came from 1035 men 60 to 73 years of age (μ = 67.0, SD = 2.6). Twin models were used to calculate heritability and the genetic and environmental correlations between them.

RESULTS

Additive genetics explained 44% to 52% of Aβ42, Aβ40, t-tau, and NfL. The Aβ42/40 ratio was not heritable. Aβ40 and Aβ42 were genetically near identical (rg  = 0.94). Both Aβ40 and Aβ42 were genetically correlated with NfL (rg  = 0.35 to 0.38), but genetically unrelated to t-tau.

DISCUSSION

Except for Aβ42/40, plasma biomarkers are heritable. Aβ40 and Aβ42 share mostly the same genetic influences, whereas genetic influences on plasma t-tau and NfL are largely unique in early old-age men. The absence of genetic associations between the Aβs and t-tau is not consistent with the amyloid cascade hypothesis.

Heritability of cognitive and emotion processing during functional MRI in a twin sample

Despite compelling evidence that brain structure is heritable, the evidence for the heritability of task-evoked brain function is less robust. Findings from previous studies are inconsistent possibly reflecting small samples and methodological variations. In a large national twin sample, we systematically evaluated heritability of task-evoked brain activity derived from functional magnetic resonance imaging. We used established standardised tasks to engage brain regions involved in cognitive and emotional functions. Heritability was evaluated across a conscious and nonconscious Facial Expressions of Emotion Task (FEET), selective attention Oddball Task, N-back task of working memory maintenance, and a Go-NoGo cognitive control task in a sample of Australian adult twins (N ranged from 136 to 226 participants depending on the task and pairs). Two methods for quantifying associations of heritability and brain activity were utilised; a multivariate independent component analysis (ICA) approach and a univariate brain region-of-interest (ROI) approach. Using ICA, we observed that a significant proportion of task-evoked brain activity was heritable, with estimates ranging from 23% to 26% for activity elicited by nonconscious facial emotion stimuli, 27% to 34% for N-back working memory maintenance and sustained attention, and 32% to 33% for selective attention in the Oddball task. Using the ROI approach, we found that activity of regions specifically implicated in emotion processing and selective attention showed significant heritability for three ROIs, including estimates of 33%-34% for the left and right amygdala in the nonconscious processing of sad faces and 29% in the medial superior prefrontal cortex for the Oddball task. Although both approaches show similar levels of heritability for the Nonconscious Faces and Oddball tasks, ICA results displayed a more extensive network of heritable brain function, including additional regions beyond the ROI analysis. Furthermore, multivariate twin modelling of both ICA networks and ROI activation suggested a mix of common genetic and unique environmental factors that contribute to the associations between networks/regions. Together, the results indicate a complex relationship between genetic factors and environmental interactions that ultimately give rise to neural activation underlying cognition and emotion.

Twinning as a risk factor for neonatal acute intestinal diseases: a case-control study

Introduction

Acute intestinal diseases (AID), including necrotizing enterocolitis and spontaneous intestinal perforation, are a group of conditions that typically present in preterm infants, and are associated with an elevated mortality and morbidity rate. The risk factors for these diseases remain largely unknown. The aim of the study is to identify the correlation between twinning and the development of AID.

Methods

A single-center retrospective case-control study was conducted. We recruited all infants with a diagnosis of AID, confirmed by anatomopathology, recovered in NICU between 2010 and 2020. Considering the rarity of the outcome, 4 matched controls for each subject were randomly chosen from the overall population of newborns. Odds Ratio (OR) and 95% Confidence Interval (CI) were calculated using a conditional logistic regression model and a multivariate model by the creation of a Directed Acyclic Graph (www.dagitty.net).

Results

The study population resulted in 65 cases and 260 controls. The two groups present similar median gestational age and mean birthweight in grams. The cases have a higher frequency of neonatal pathology (defined as at least one of patent ductus arteriosus, early or late sepsis, severe respiratory distress) (84.6% vs. 51.9%), medically assisted procreation (33.8% vs. 18.8%) and periventricular leukomalacia (10.8% vs. 2.7%), and a lower frequency of steroids prophylaxis (67.7% vs. 86.9%). About 50% of cases needed surgery. The OR for the direct effect were difference from one using logistic regression booth without and with repeated measures statements: from 1.14 to 4.21 (p = .019) and from 1.16 to 4.29 (p = .016), respectively.

Conclusions

Our study suggests that twinning may be a risk factor for the development of AID. Due to the small number of cases observed, further studies on larger populations are needed.

Twins with meningitis due to Neisseria meningitidis

Introduction

The incidence of invasive meningococcal disease is highest in infants and young children.

Case report

Twin infants diagnosed two days apart with meningitis due to N. meningitidis serogroup B are presented.

Conclusions

There has never been a report of concurrent meningococcal meningitis in twin brothers. We wanted to highlight the high likelihood of meningococcal transmission through household contacts and the importance of antibiotic prophylaxis and meningococcal vaccination recommendations for close contacts of these cases.

Glycemic control and neonatal outcomes in twin pregnancies with gestational diabetes mellitus

BACKGROUND

Preliminary data suggest that strict glycemic control in twin pregnancies with gestational diabetes mellitus may not improve outcomes but might increase the risk of fetal growth restriction.

OBJECTIVE

This study aimed to investigate the association of maternal glycemic control with the risk of gestational diabetes mellitus-related complications and small for gestational age in twin pregnancies complicated by gestational diabetes mellitus.

STUDY DESIGN

This was a retrospective cohort study of all patients with a twin pregnancy complicated by gestational diabetes mellitus in a single tertiary center between 2011 and 2020, and a matched control group of patients with a twin pregnancy without gestational diabetes mellitus in a 1:3 ratio. The exposure was the level of glycemic control, described as the proportion of fasting, postprandial, and overall glucose values within target. Good glycemic control was defined as a proportion of values within target above the 50th percentile. The first coprimary outcome was a composite variable of neonatal morbidity, defined as at least 1 of the following: birthweight >90th centile for gestational age, hypoglycemia requiring treatment, jaundice requiring phototherapy, birth trauma, or admission to the neonatal intensive care unit at term. A second coprimary outcome was small for gestational age, defined as birthweight <10th centile or <3rd centile for gestational age. Associations between the level of glycemic control and the study outcomes were estimated using logistic regression analysis and were expressed as adjusted odds ratio with 95% confidence interval.

RESULTS

A total of 105 patients with gestational diabetes mellitus in a twin pregnancy met the study criteria. The overall rate of the primary outcome was 32.4% (34/105), and the overall proportion of pregnancies with a small for gestational age newborn at birth was 43.8% (46/105). Good glycemic control was not associated with a reduction in the risk of composite neonatal morbidity when compared with suboptimal glycemic control (32.1% vs 32.7%; adjusted odds ratio, 2.06 [95% confidence interval, 0.77-5.49]). However, good glycemic control was associated with higher odds of small for gestational age compared with nongestational diabetes mellitus pregnancies, especially in the subgroup of diet-treated gestational diabetes mellitus (65.5% vs 34.0%, respectively; adjusted odds ratio, 4.17 [95% confidence interval, 1.74-10.01] for small for gestational age <10th centile; and 24.1% vs 7.0%, respectively; adjusted odds ratio, 3.97 [95% confidence interval, 1.42-11.10] for small for gestational age <3rd centile). In contrast, the rate of small for gestational age in gestational diabetes mellitus pregnancies with suboptimal control was not considerably different when compared with non-gestational diabetes mellitus pregnancies. In addition, in cases of diet-treated gestational diabetes mellitus, good glycemic control was associated with a left-shift of the distribution of birthweight centiles, whereas the distribution of birthweight centiles among gestational diabetes mellitus pregnancies with suboptimal control was similar to that of nongestational diabetes mellitus pregnancies.

CONCLUSION

In patients with gestational diabetes mellitus in a twin pregnancy, good glycemic control is not associated with a reduction in the risk of gestational diabetes mellitus-related complications but may increase the risk of a small for gestational age newborn in the subgroup of patients with mild (diet-treated) gestational diabetes mellitus. These findings further question whether the gestational diabetes mellitus glycemic targets used in singleton pregnancies also apply to twin pregnancies and support the concern that applying the same diagnostic criteria and glycemic targets in twin pregnancies may result in overdiagnosis and overtreatment of gestational diabetes mellitus and potential neonatal harm.

National and international guidelines on the management of twin pregnancies: a comparative review

Twin gestations are associated with increased risk of pregnancy complications. However, high-quality evidence regarding the management of twin pregnancies is limited, often resulting in inconsistencies in the recommendations of various national and international professional societies. In addition, some recommendations related to the management of twin gestations are often missing from the clinical guidelines dedicated to twin pregnancies and are instead included in the practice guidelines on specific pregnancy complications (eg, preterm birth) of the same professional society. This can make it challenging for care providers to easily identify and compare recommendations for the management of twin pregnancies. This study aimed to identify, summarize, and compare the recommendations of selected professional societies from high-income countries on the management of twin pregnancies, highlighting areas of both consensus and controversy. We reviewed clinical practice guidelines of selected major professional societies that were either specific to twin pregnancies or were focused on pregnancy complications or aspects of antenatal care that may be relevant for twin pregnancies. We decided a priori to include clinical guidelines from 7 high-income countries (United States, Canada, United Kingdom, France, Germany, and Australia and New Zealand grouped together) and from 2 international societies (International Society of Ultrasound in Obstetrics and Gynecology and the International Federation of Gynecology and Obstetrics). We identified recommendations regarding the following care areas: first-trimester care, antenatal surveillance, preterm birth and other pregnancy complications (preeclampsia, fetal growth restriction, and gestational diabetes mellitus), and timing and mode of delivery. We identified 28 guidelines published by 11 professional societies from the 7 countries and 2 international societies. Thirteen of these guidelines focus on twin pregnancies, whereas the other 16 focus on specific pregnancy complications predominantly in singletons but also include some recommendations for twin pregnancies. Most of the guidelines are recent, with 15 of the 29 guidelines published over the past 3 years. We identified considerable disagreement among guidelines, primarily in 4 key areas: screening and prevention of preterm birth, using aspirin to prevent preeclampsia, defining fetal growth restriction, and the timing of delivery. In addition, there is limited guidance on several important areas, including the implications of the "vanishing twin" phenomenon, technical aspects and risks of invasive procedures, nutrition and weight gain, physical and sexual activity, the optimal growth chart to be used in twin pregnancies, the diagnosis and management of gestational diabetes mellitus, and intrapartum care.This consolidation of key recommendations across several clinical practice guidelines can assist healthcare providers in accessing and comparing recommendations on the management of twin pregnancies and identifies high-priority areas for future research based on either continued disagreement among societies or limited current evidence to guide care.

A prediction tool for mode of delivery in twin pregnancies-a secondary analysis of the Twin Birth Study

BACKGROUND

One of the controversies regarding the management of twin gestations relates to the mode of delivery. Currently, counseling regarding the mode of delivery and the chance of successful vaginal twin delivery is based on the average risk for intrapartum cesarean delivery in the general population of twin pregnancies. Decision support tools that provide an individualized risk for intrapartum cesarean delivery based on the unique characteristics of each patient can improve counseling and decision-making regarding the choice of mode of delivery in twin pregnancies.

OBJECTIVE

This study aimed to develop and validate a prediction model to determine the risk for intrapartum cesarean delivery in twin pregnancies.

STUDY DESIGN

In this secondary analysis of the Twin Birth Study, a multicenter randomized controlled trial, we considered the subgroup of individuals who underwent a trial of vaginal delivery. Candidate predictors included maternal age, parity, previous cesarean delivery, conception method, chorionicity, diabetes and hypertension in pregnancy, gestational age at birth, the onset of labor, presentation of the second twin, sonographic fetal weight estimation, and fetal sex. The co-primary outcomes were overall intrapartum cesarean delivery and cesarean delivery of the second twin. Multivariable logistic regression models were used to estimate the probability of the study outcomes. Model performance was evaluated using measures of discrimination (the area under the receiver operating characteristic curve), calibration, and predictive accuracy. Internal validation was performed using the bootstrap resampling technique.

RESULTS

A total of 1221 individuals met the study criteria. The rate of overall intrapartum cesarean delivery and cesarean delivery for the second twin was 25.4% and 5.7%, respectively. The most contributory predictor variables were nulliparity, term birth (≥37 weeks), a noncephalic presentation of the second twin, previous cesarean delivery, and labor induction. The models for overall intrapartum cesarean delivery and cesarean delivery of the second twin had good overall discriminatory accuracy (area under the receiver operating characteristic curve, 0.720; 95% confidence interval, 0.688-0.752 and 0.736; 95% confidence interval, 0.669-0.803, respectively) and calibration (as illustrated by the calibration plot and Brier scores of 0.168; 95% confidence interval, 0.156-0.180 and 0.051; 95% confidence interval, 0.040-0.061, respectively). The models achieved good specificity (66.7% and 81.6%, respectively), high negative predictive value (86.0% and 96.9%, respectively), and moderate sensitivity (68.1% and 57.1%, respectively).

CONCLUSION

The prediction models developed in this study may assist care providers in counseling individuals regarding the optimal timing and mode of delivery in twin pregnancies by providing individualized estimates of the risk for intrapartum cesarean delivery.

Genetic and environmental architecture of synaesthesia and its association with the autism spectrum-a twin study

Synaesthesia is a sensory phenomenon where external stimuli, such as sounds or letters, trigger additional sensations (e.g. colours). Synaesthesia aggregates in families but its heritability is unknown. The phenomenon is more common in people on the autism spectrum compared with the general population and associated with higher autistic traits. Using classical twin design, we assessed the heritability of individual differences in self-reported synaesthesia and the genetic and environmental contributions to their association with autistic traits within a population twin cohort (n = 4262, age = 18 years). We estimated individual differences in synaesthesia to be heritable and influenced by environmental factors not shared between twins. The association between individual differences in synaesthesia and autistic traits was estimated to be predominantly under genetic influence and seemed to be mainly driven by non-social autistic traits (repetitive behaviours, restricted interests and attention to detail). Our study suggests that the link between synaesthesia and autism might reside in shared genetic causes, related to non-social autistic traits such as alterations in perception. Future studies building on these findings may attempt to identify specific groups of genes that influence both autism, synaesthesia and perception.

The Characteristic of {101¯2}<101¯1¯> Twin of Ti-10V-2Fe-3Al under Planar Wave Detonation

The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to the limited slip system in this phase. α grains are mainly rotated from {101¯0} to {0002} during the deformation due to the {101¯2}<101¯1¯> twin. Twin variant selection is found in this study, and the orientation of all {101¯2} twins is oriented at {0002} in different α grains with different deformation degrees. The twin variant selection is well explained based on the strain relaxation along the loading axis and the Schmid factor for twinning shear.

Selective intrauterine growth restriction without concomitant twin-to-twin transfusion syndrome, natural history, and risk factors for fetal death: A systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the natural history of selective intrauterine growth restriction in monochorionic twin pregnancies based on the Gratacós classification, including progression of, improvement in, or stability of umbilical artery Dopplers and progression to twin-to-twin transfusion syndrome or twin anemia polycythemia syndrome. We also aimed to investigate risk factors for smaller twin demise.

DATA SOURCES

A systematic search was performed to identify relevant studies published in English up to June 2022 using the databases PubMed, Scopus, and Web of Science STUDY ELIGIBILITY: We used retrospective and prospective studies published in English that reported on selective intrauterine growth restriction without concomitant twin-to-twin transfusion syndrome.

STUDY APPRAISAL AND SYNTHESIS METHODS

Articles that investigated selective intrauterine growth restriction progression and outcomes by umbilical artery Doppler end-diastolic flow (Gratacós classification) were included. Type I included selective intrauterine growth restriction cases with positive end-diastolic flow, type II included those cases with persistently absent end-diastolic flow, and type III included cases with intermittent absent or reversed end-diastolic flow. Pregnancies in which a diagnosis of twin-to-twin transfusion syndrome or twin anemia polycythemia sequence was made before the diagnosis of selective intrauterine growth restriction were not included in the analysis. A random effects model was used to pool the odds ratios and the corresponding 95% confidence intervals. Heterogeneity was assessed using the I2 value.

RESULTS

A total of 17 studies encompassing 2748 monochorionic pregnancies complicated by selective intrauterine growth restriction were included in the analysis. The incidence of stable, deteriorating, or improving umbilical artery Dopplers in type I cases was 68% (95% confidence interval, 26-89), 23% (95% confidence interval, 7-40), and 9% (95% confidence interval, 0.0-100), respectively. In type II cases, the incidence was 40% (95% confidence interval, 18-81), 50% (95% confidence interval, 23-82), and 10% (95% confidence interval, 4-37), respectively, and in type III cases, the incidence was 55% (95% confidence interval, 2-99), 23% (95% confidence interval, 9-43), and 22% (95% confidence interval, 6-54), respectively. The risk for progression to twin-to-twin transfusion syndrome was comparable between type I (7%) and type III (9%) cases and occurred in 4% (95% confidence interval, 0-67) of type II cases with no significant subgroup differences. Progression to twin anemia polycythemia syndrome was highest in type I cases (12%) and comparable between type II (2%) and III (1%) cases with no significant subgroup differences. Risk factors for smaller twin demise were earlier gestational age at diagnosis (mean difference, -2.69 weeks; 95% confidence interval, -4.94 to -0.45; I2, 45%), larger intertwin weight discordance (mean difference, 34%; 95% confidence interval, 1.35-5.38; I2, 28%), deterioration of umbilical artery Dopplers for each of type II and III cases (odds ratio, 3.05; 95% confidence interval, 1.36-6.84; I2, 24%; and odds ratio, 4.5; 95% confidence interval, 2.31-8.77; I2, 0.0%, respectively), and absent or reversed ductus venosus a-wave for each of type II and III cases (odds ratio, 3.35; 95% confidence interval, 2.28-4.93; I2, 0.0%; and odds ratio, 2.36; 95% confidence interval, 1.08-5.13; I2, 0.0%, respectively). Progression to twin-to-twin transfusion syndrome was not significantly associated with smaller twin demise for each of type II and III selective intrauterine growth restriction cases.

CONCLUSION

These findings improve our understanding of the natural history of the types of selective intrauterine growth restriction and of the predictors of smaller twin demise in type II and III selective intrauterine growth restriction cases. The current data provide vital counseling points and support the need for modifications of the current selective intrauterine growth restriction classification system to include the variations in umbilical artery and ductus venosus Dopplers to better identify a cohort that might benefit from fetal intervention for which future multicenter prospective randomized trials are needed.

Degree of leukochimerism with calf age in Angus-crossbred twin sets

Twinning in cattle is infrequent and usually undesired. It can result in an increased occurrence of abortion and dystocia, reduced calf survival and a high likelihood of freemartinism in mixed-sex twins. Twin gestations are also commonly associated with the formation of placental vascular anastomoses (PVA) between twins. Through PVA they share blood, hormones (leading to freemartinism in mixed sex twins) and hematopoietic stem cells, which are the progenitors of white blood cells. The sharing of stem cells between twins can result in leukochimeric twin sets. These are twins that have white blood cells derived from both self and the co-twin owing to the fetal migration of hematopoietic stem cells from the extraembryonic mesoderm of the yolk sac to final sites like bone marrow and thymus. This study examined the degree to which this leukochimerism changes with age. DNA was extracted from hair bulbs containing mesenchymal dermal papilla to determine the individual's true genotype and blood samples were obtained at six time points from 1 week to 8 months of age to assess leukochimerism. Samples were genotyped using a medium density SNP chip, and quantitative estimates of allele frequency were determined using SNPs for which members of a twin set had alternative homozygous genotypes. The results indicate statistically significant changes in the proportion of self and co-twin with age and suggest that by 2-4 months of age the genotypic mix in white blood cells represents the hematopoetic stem cell population resident in the individual (i.e. permanently found in thymus and bone marrow).

Preterm management of sickle cell crisis in a twin pregnancy with suboptimal antenatal care in a primary healthcare facility: A case report from Cameroon and literature review

Key Clinical Message

Twin pregnancies in homozygous sickle cell patients are not only uncommon in our setting but are most often associated with adverse maternal-fetal outcomes especially in primary healthcare facilities where most of these cases initially present due to financial constraints, though lacking the necessary technical platform (including blood banks) to properly manage them.

Abstract

We are reporting the case of the preterm management of sickle cell crises in a twin pregnancy with poor antenatal care uptake in a primary healthcare facility devoid of a blood bank in Cameroon. Ngungi Fely, a 21-year-old HbSS patient, of the Bakweri tribe G3P0020, blood group O rhesus positive, was admitted at our health facility at 33 3/7 weeks' gestation with twin pregnancy, clinical anemia (hemoglobin 3.3 g/dL), the pulse rate of 123 beats/min, the respiratory rate of 38 breaths per min, the temperature of 39.2°C, and altered state of consciousness. She has a history of two spontaneous abortions (16 and 18 weeks' gestation) and has attended three antenatal care (ANC) visits (18, 24, and 28 weeks' gestation) for the index pregnancy. She underwent cesarean delivery of two live-born babies at 35 4/7 weeks' gestation and received 9 units of compatible blood (before, during, and after the cesarean) partly with the help of the "Blood Track Program" (which uses text messages to seek blood donors). The babies were referred to a secondary healthcare facility and the mother and babies' outcomes were uneventful. Sickle cell disease (SCD) in pregnancy is difficult to manage in primary care settings in Cameroon because of a poor technical platform. A multidisciplinary approach to the management of SCD in pregnancy is the mainstay in secondary and tertiary healthcare centers. The "Blood Track Program" is a good initiative that should be extended nationwide in Cameroon to reduce the burden of acquiring blood for transfusion, particularly in primary care centers devoid of blood banks.

Cell-free DNA screening for trisomy 21 in twin pregnancy: a large multicenter cohort study

BACKGROUND

Analysis of cell-free DNA from maternal blood provides effective screening for trisomy 21 in singleton pregnancies. Data on cell-free DNA screening in twin gestations are promising although limited. In previous twin studies, cell-free DNA screening was primarily performed in the second trimester and many studies did not report chorionicity.

OBJECTIVE

This study aimed to evaluate the screening performance of cell-free DNA for trisomy 21 in twin pregnancies in a large, diverse cohort. A secondary aim was to evaluate screening performance for trisomy 18 and trisomy 13.

STUDY DESIGN

This was a retrospective cohort study of twin pregnancies from 17 centers for which cell-free DNA screening was performed from December 2011 to February 2020 by one laboratory using massively parallel sequencing technology. Medical record review was conducted for all newborns and data on the birth outcome, the presence of any congenital abnormalities, phenotypic appearance at birth, and any chromosomal testing that was undertaken in the antenatal or postnatal period were extracted. Cases with a possible fetal chromosomal abnormality with no genetic test results were reviewed by a committee of maternal-fetal medicine geneticists. Cases with a vanishing twin and inadequate follow-up information were excluded. A minimum of 35 confirmed cases of trisomy 21 was required to capture a sensitivity of at least 90% with a prevalence of at least 1.9% with 80% power. Test characteristics were calculated for each outcome.

RESULTS

A total of 1764 samples were sent for twin cell-free DNA screening. Of those, 78 cases with a vanishing twin and 239 cases with inadequate follow-up were excluded, leaving a total of 1447 cases for inclusion in the analysis. The median maternal age was 35 years and the median gestational age at cell-free DNA testing was 12.3 weeks. In total, 81% of the twins were dichorionic. The median fetal fraction was 12.4%. Trisomy 21 was detected in 41 of 42 pregnancies, yielding a detection rate of 97.6% (95% confidence interval, 83.8-99.7). There was 1 false negative and no false positive cases. Trisomy 21 was detected in 38 out of 39 dichorionic twin pregnancies, yielding a detection rate of 97.4% (95% confidence interval, 82.6-99.7). Trisomy 18 was detected in 10 of the 10 affected pregnancies. There was 1 false positive case. Trisomy 13 was detected in 4 of the 5 cases, yielding a detection rate of 80% (95% confidence interval, 11.1-99.2). There was one false negative and no false positive cases. The nonreportable rate was low at 3.9 %.

CONCLUSION

Cell-free DNA testing is effective in screening for trisomy 21 in twin gestations from the first trimester of pregnancy. Detection of trisomy 21 was high in dichorionic and monochorionic twins, and the nonreportable result rates were low. This study included high numbers of cases of trisomy 18 and 13 when compared with the current literature. Although screening for these conditions in twins seems to be promising, the numbers were too small to make definitive conclusions regarding the screening efficacy for these conditions. It is possible that cell-free DNA testing performance may differ among laboratories and vary with screening methodologies.

A new care pathway to optimize gestational weight gain in twin pregnancies

BACKGROUND

Maternal gestational weight gain is an important determinant of pregnancy outcomes and may have an even greater role in twin pregnancies because of their higher rate of pregnancy complications and greater nutritional demands. However, data on the optimal week-specific gestational weight gain in twin pregnancies and on interventions that should be applied in cases of inadequate gestational weight gain are limited.

OBJECTIVE

This study aimed to determine whether a new care pathway that involves monitoring gestational weight gain using a week-specific chart, along with a standardized protocol for managing cases with inadequate gestational weight gain, can optimize maternal gestational weight gain in twin pregnancies.

METHODS

In this study, patients with twin pregnancies followed in a single tertiary center between February 2021 and May 2022 were exposed to the new care pathway (postintervention group). Gestational weight gain and clinical outcomes were compared with those of a previously described cohort of patients with twins followed in our clinic before the implementation of the new care pathway (preintervention group). The new care pathway targeted patients and care providers and included educational material, a newly developed body mass index group-specific gestational weight gain chart, and a stepwise management algorithm in cases of inadequate gestational weight gain. The body mass index group-specific gestational weight gain charts were divided into 3 zones: (1) green zone (optimal gestational weight gain at 25th-75th centiles); (2) yellow zone (suboptimal gestational weight gain at 5th-24th or 76th-95th centiles); and (3) gray zone (abnormal gestational weight gain, at <5th or >95th centile). The primary outcome was the overall proportion of patients achieving optimal gestational weight gain at birth.

RESULTS

A total of 123 patients were exposed to the new care pathway and were compared with 1079 patients from the preintervention period. Patients in the postintervention group were more likely to achieve optimal gestational weight gain at birth (60.2% vs 47.7%; adjusted odds ratio, 1.91; 95% confidence interval, 1.28-2.86) and were less likely to achieve low-suboptimal gestational weight gain (7.3% vs 14.7%; adjusted odds ratio, 0.41; 95% confidence interval, 0.20-0.85) or any suboptimal gestational weight gain (26.8% vs 34.8%; adjusted odds ratio, 0.60; 95% confidence interval, 0.39-0.93) at birth. In addition, patients in the postintervention group were less likely to have low-abnormal gestational weight gain anytime during gestation (18.9% vs 29.1%; P=.017) and were more likely to have normal gestational weight gain throughout pregnancy (21.3% vs 14.0%; P=.031) or high-abnormal gestational weight gain anytime during gestation (18.0% vs 11.1%; P=.025), suggesting that in comparison with standard care, the new care pathway is more effective in preventing patients from moving into the low-abnormal zone than the high-abnormal zone. Furthermore, the new care pathway was more effective than standard care in correcting high-suboptimal gestational weight gain and high-abnormal gestational weight gain.

CONCLUSION

Our findings suggest that the new care pathway may be effective in optimizing maternal gestational weight gain in twin gestations, which may in turn contribute to better clinical outcomes. This is a simple, low-cost intervention that can be easily disseminated among providers caring for patients with twin pregnancies.

Heritability and circulating concentrations of pregnancy-associated plasma protein-A and stanniocalcin-2 in elderly monozygotic and dizygotic twins

Introduction

Pregnancy-associated plasma protein-A (PAPP-A) is an IGF-activating enzyme suggested to influence aging-related diseases. However, knowledge on serum PAPP-A concentration and regulation in elderly subjects is limited. Therefore, we measured serum PAPP-A in elderly same-sex monozygotic (MZ) and dizygotic (DZ) twins, as this allowed us to describe the age-relationship of PAPP-A, and to test the hypothesis that serum PAPP-A concentrations are genetically determined. As PAPP-A is functionally related to stanniocalcin-2 (STC2), an endogenous PAPP-A inhibitor, we included measurements on STC2 as well as IGF-I and IGF-II.

Methods

The twin cohort contained 596 subjects (250 MZ twins, 346 DZ twins), whereof 33% were males. The age ranged from 73.2 to 94.3 (mean 78.8) years. Serum was analyzed for PAPP-A, STC2, IGF-I, and IGF-II by commercial immunoassays.

Results

In the twin cohort, PAPP-A increased with age (r=0.19; P<0.05), whereas IGF-I decreased (r=-0.12; P<0.05). Neither STC2 nor IGF-II showed any age relationship. When analyzed according to sex, PAPP-A correlated positively with age in males (r=0.18; P<0.05) and females (r=0.25; P<0.01), whereas IGF-I correlated inversely in females only (r=-0.15; P<0.01). Males had higher levels of PAPP-A (29%), STC2 (18%) and IGF-I (19%), whereas serum IGF-II was 28% higher in females (all P<0.001). For all four proteins, within-pair correlations were significantly higher for MZ twins than for DZ twins, and they demonstrated substantial and significant heritability, which after adjustment for age and sex averaged 59% for PAPP-A, 66% for STC2, 58% for IGF-I, and 52% for IGF-II.

Discussion

This twin study confirms our hypothesis that the heritability of PAPP-A serum concentrations is substantial, and the same is true for STC2. As regards the age relationship, PAPP-A increases with age, whereas STC2 remains unchanged, thereby supporting the idea that the ability of STC2 to inhibit PAPP-A enzymatic activity decreases with increasing age.

Infertility Treatments Resulting in Twin Pregnancy: Does It Increase the Risk for Future Childhood Malignancy

Background: Controversy exists in the literature regarding the possible association between infertility treatments in singleton pregnancies and long-term risk for childhood malignancy. Data regarding infertility treatments in twins and long-term childhood malignancies are scarce. Objective: We sought to investigate whether twins conceived following infertility treatments are at an increased risk for childhood malignancy. Study design: A population-based retrospective cohort study, comparing the risk for future childhood malignancy in twins conceived by infertility treatments (in vitro fertilization and ovulation induction) and those who were conceived spontaneously. Deliveries occurred between the years 1991 and 2021 in a tertiary medical center. A Kaplan-Meier survival curve was used to compare the cumulative incidence of childhood malignancies, and a Cox proportional hazards model was constructed to control for confounders. Results: During the study period, 11,986 twins met the inclusion criteria; 2910 (24.3%) were born following infertility treatments. No statistically significant differences were noted between the groups comparing the rate (per 1000) of childhood malignancies (2.0 in the infertility treatments group vs. 2.2 in the comparison group, OR 1.04, 95% CI 0.41-2.62; p = 0.93). Likewise, the cumulative incidence over time was comparable between the groups (log-rank test, p = 0.87). In a Cox regression model, controlling for maternal and gestational age, no significant differences in childhood malignancies were noted between the groups (adjusted HR = 0.82, 95% CI 0.49-1.39, p = 0.47). Conclusions: In our population, twins conceived following infertility treatments are not at an increased risk for childhood malignancies.

Comparison of renal artery Doppler parameters of monochorionic diamniotic twin pregnancies with and without twin-to-twin transfusion syndrome

Background

Monochorionic diamniotic (MCDA) twin pregnancies are considered high-risk for several reasons, especially the risk of twin-to-twin transfusion syndrome (TTTS). Renal artery Doppler (RAD) is reported as a useful tool for predicting oligohydramnios in singleton pregnancies. We aimed to compare the RAD indices between MCDA twins with and without TTTS.

Materials and Methods

In this case-control study, all pregnant women aged 18-38 years, with gestational age ≥ 18 weeks, who were referred to two Prenatal Clinics, Alzahra and Beheshti Educational Hospitals, affiliated to Isfahan University of Medical Sciences, Isfahan, Iran, October 2020-March 2022 were enrolled; the women with MCDA twin pregnancies complicated by TTTS (case group, n = 12) and without TTTS (control group, n = 24). For each twin, biometric analysis, fetal weight, and Doppler study of fetal arteries, including RAD, middle cerebral artery (MCA), umbilical artery, and ductus venosus were performed. Peak systolic velocity, Pulsatility index (PI), resistance index (RI), and systole/diastole (S/D) were measured for all arteries.

Results

The donors of the case group had a lower mean MCA S/D (4.48 ± 1.89) than the control group (6.48 ± 1.97) (P = 0.01) and higher mean umbilical parameters, including PI, RI, and S/D (P < 0.05). The recipients of the case group had a lower mean renal PI than the control (P = 0.008) and lower mean MCA PI, RI, and S/D (P < 0.05). The donor group had a higher mean umbilical RI and S/D than the recipient twin, while the mean fetal weight of the recipient group was higher (P < 0.05).

Conclusion

Comparing the RAD parameters between the twins with and without TTTS in the present study did not identify significant results, which rejected the primary hypothesis. Among all RAD parameters, the only significant difference observed in the present study was the lower RAD PI in RT, which cannot suggest this measurement as a valuable tool for the prediction of TTTS in MCDA twins. Therefore, the results of the present study failed to show the additional value of RAD, compared with the conventional Doppler examination of fetal arteries. Further studies are required to prove this conclusion.

Reproducibility of the digital palate in forensic investigations, a two-year retrospective cohort study of twins

OBJECTIVES

The palatal scans of the same individuals were compared after two years to assess forensic reproducibility. The effect of orthodontic treatment, the comparison area and the digitization approach were investigated.

METHODS

The palate was scanned in 20 pairs of monozygotic twins by an intraoral scanner (IOS) three times to assess repeatability. They were rescanned two years later by two different IOSs. An elastic impression and a plaster model were also made and scanned by a laboratory scanner (indirect digitization). Mean absolute distance between scans was compared after best-fit alignment. Scans from the two sessions were compared to evaluate the combined effect of aging, orthodontic treatment and different digitization methods (forensic reproducibility). Additionally, the scans of different digitization methods from the second session were compared (technical reproducibility). The between-siblings difference was compared in the two sessions to evaluate the effect of aging on palatal morphology.

RESULTS

The anterior palatal area showed significantly better repeatability and forensic reproducibility than the whole palate (p<0.001), but orthodontic treatment had no effect. Indirect digitization produced lower forensic and technical reproducibility than IOSs. For IOSs, repeatability (22 µm) was significantly (p<0.001) better than either forensic (75-77 µm) or technical reproducibility (37 µm). No significant changes were observed from the first to the second session in the between-sibling comparison. The closest between-sibling value (239 µm) considerably exceeded the highest forensic reproducibility value (141 µm).

CONCLUSIONS

Reproducibility is acceptable between the different IOSs, even two years apart, but is poor between IOS and indirect digitization. The anterior palate is relatively stable in young adults.

CLINICAL SIGNIFICANCE

Intraoral scanning of the anterior palatal area has superior reproducibility, regardless of the IOS brand. Therefore, the IOS method could be suitable for identifying humans through anterior palatal morphology. However, the digitization of elastic impressions or plaster models had low reproducibility, preventing their application for forensic purposes.

The Effect of Cooling Rate on Crystallographic Features of Phase Transformations in Zr-2.5Nb

Zirconium (Zr) alloys are utilized as structural components for the cores of nuclear reactors due to the excellent combination of their mechanical properties and corrosion resistance under intense neutron irradiation conditions in water. The characteristics of microstructures formed during heat treatments play a crucial role in obtaining the operational performance of parts made from Zr alloys. This study investigates the morphological features of (α + β)-microstructures in the Zr-2.5Nb alloy, as well as the crystallographic relationships between α- and β-phases. These relationships are induced by the β→α(α″) displacive transformation that occurs during water quenching (WQ) and the diffusion-eutectoid transformation that takes place during furnace cooling (FC). To conduct this analysis, samples solution treated at 920 °C were examined using EBSD and TEM. The experimental distribution of α/β-misorientations for both cooling regimes deviates from the Burgers orientation relationship (BOR) at a discrete set of angles close to 0, 29, 35, and 43°. The experimental α/β-misorientation spectra are confirmed by crystallographic calculations for the β→α→β-transformation path based on the BOR. Similar spectra of misorientation angle distribution in α-phase and between α and β phases in Zr-2.5Nb after WQ and FC point to similar transformation mechanisms and the significant role of shear and shuffle in β→α-transformation.

Sonographically Positive Fetal Heartbeat in Unilateral Tubal Twin Pregnancy as a Rare Case With Literature Review

Ectopic pregnancies occur when a fertilized egg implants outside the uterus, usually in the fallopian tube. Twin ectopic pregnancies are rare and pose significant diagnostic and management challenges. This case report presents the clinical details and management of a unilateral twin ectopic pregnancy in a 31-year-old female patient. The purpose of this report is to highlight the complexities associated with the diagnosis and management of this uncommon condition. In this case, we performed the left salpingectomy. We confirmed pathologically and histologically in pregnancy in the same tube.

Secular Trends of Birth Weight in Twins and Singletons in South Korea from 2000 to 2020

Whether the decline of birth weight (BW) reported in developed countries in the early 2000s is ongoing remains unknown. Furthermore, despite recent sharp increases in twin births, comparing secular trends of BW between singletons and twins is difficult, as studies have rarely examined secular trends of BW in twins and singletons simultaneously. Therefore, this study aimed to investigate the most recent 20-year trends (2000-2020) of BW in twins and singletons in South Korea. Annual natality files from 2000 to 2020 obtained from the Korean Statistical Information Service were analyzed. A yearly decrease of BW was 3 g among singletons and 5 to 6 g in twins from 2000 to 2020, indicating a widening gap of BW between twins and singletons with increasing years. Gestational age (GA) also decreased in twins and singletons with yearly decreases of 0.28 days in singletons and 0.41 days in twins. Whereas BW decreased in term (GA ≥ 37 weeks), and very preterm groups (28 weeks ≤ GA < 32 weeks) from 2000 to 2020 in twins and singletons, it increased in moderate to late preterm (32 weeks ≤ GA < 37 weeks) groups, indicating a non-linear relationship between BW and GA. The prevalence of macrosomia (BW > 4000 g) in singletons decreased from 2000 to 2020, whereas low birth weight (LBW; BW < 2500 g) increased in twins and singletons. LBW is associated with adverse health outcomes. Effective public health strategies aiming at reduction in the incidence of LBW in the population should be developed.

A Rare Case of Postoperative Encephalopathy in Twin

The clinical picture of encephalopathy invites a broad differential with multiple etiologies. It is with judicious history, hospital course, lab testing, and imaging that the ultimate cause is identified. We present a unique case of identical twins who share a similar clinical presentation of postoperative encephalopathy. The striking similarities in both twins suggest a genetic component requiring further research to identify patients who are genetically predisposed.

Associations between polygenic risk of substance use and use disorder and alcohol, cannabis, and nicotine use in adolescence and young adulthood in a longitudinal twin study

BACKGROUND

Recent well-powered genome-wide association studies have enhanced prediction of substance use outcomes via polygenic scores (PGSs). Here, we test (1) whether these scores contribute to prediction over-and-above family history, (2) the extent to which PGS prediction reflects inherited genetic variation v. demography (population stratification and assortative mating) and indirect genetic effects of parents (genetic nurture), and (3) whether PGS prediction is mediated by behavioral disinhibition prior to substance use onset.

METHODS

PGSs for alcohol, cannabis, and nicotine use/use disorder were calculated for Minnesota Twin Family Study participants (N = 2483, 1565 monozygotic/918 dizygotic). Twins' parents were assessed for histories of substance use disorder. Twins were assessed for behavioral disinhibition at age 11 and substance use from ages 14 to 24. PGS prediction of substance use was examined using linear mixed-effects, within-twin pair, and structural equation models.

RESULTS

Nearly all PGS measures were associated with multiple types of substance use independently of family history. However, most within-pair PGS prediction estimates were substantially smaller than the corresponding between-pair estimates, suggesting that prediction is driven in part by demography and indirect genetic effects of parents. Path analyses indicated the effects of both PGSs and family history on substance use were mediated via disinhibition in preadolescence.

CONCLUSIONS

PGSs capturing risk of substance use and use disorder can be combined with family history measures to augment prediction of substance use outcomes. Results highlight indirect sources of genetic associations and preadolescent elevations in behavioral disinhibition as two routes through which these scores may relate to substance use.

Nonlinear Catch-Up Growth in Height, Weight, and Head Circumference from Birth to Adolescence: A Longitudinal Twin Study

Owing to high rates of prenatal complications, twins are, on average, substantially smaller than population norms on physical measurements including height, weight, and head circumference at birth. By early childhood, twins are physically average. This study is the first to explore the process of catch-up growth by fitting asymptotic growth models to age-standardized height, weight, and head circumference measurements in a community sample of twins ( n  = 1,281, 52.3% female) followed at up to 17 time points from birth to 15 years. Catch-up growth was rapid over the first year and plateaued around the population mean by early childhood. Shared environmental factors accounted for the majority of individual differences in initial physical size (57.7%-65.5%), whereas additive genetic factors accounted for the majority of individual differences in the upper asymptotes of height, weight, and head circumference (73.4%-92.6%). Both additive genetic and shared environmental factors were associated with variance in how quickly twins caught up. Gestational age and family SES emerged as important environmental correlates of physical catch-up growth.

Application of Color Doppler with 3- and 4-Dimensional Ultrasonography in the Prenatal Evaluation of Fetal Extracardiac and Placental Abnormalities

Using color Doppler flow imaging or high-definition flow imaging with three-dimensional volume or spatio-temporal image correlation (STIC) in the glass-body mode allows displaying both gray-scale and color information of the heart cycle-related flow events and vessel spatial relationship. Conventionally, STIC in the glass-body mode has been used to examine the fetal heart and assess heart defects. Recently, a novel application of STIC in the visualization of abdominal precordial veins and intraplacental vascularization in singleton pregnancies has been reported. The aim of this present review is to discuss the use of color Doppler with three- and four-dimensional ultrasonography in the evaluation of extracardiac, placental, umbilical cord and twin abnormalities with examples. The glass-body mode is complementary to conventional 2D ultrasonography. Further studies are required to investigate use of the glass-body mode in the assessment of intraplacental vascularization in singleton and twin pregnancies.

Soft, malleable double diamond twin

A twin boundary (TB) is a common low energy planar defect in crystals including those with the atomic diamond structure (C, Si, Ge, etc.). We study twins in a self-assembled soft matter block copolymer (BCP) supramolecular crystal having the double diamond (DD) structure, consisting of two translationally shifted, interpenetrating diamond networks of the minority polydimethyl siloxane block embedded in a polystyrene block matrix. The coherent, low energy, mirror-symmetric double tubular network twin has one minority block network with its nodes offset from the (222) TB plane, while nodes of the second network lie in the plane of the boundary. The offset network, although at a scale about a factor of 10³ larger, has precisely the same geometry and symmetry as a (111) twin in atomic single diamond where the tetrahedral units spanning the TB retain nearly the same strut (bond) lengths and strut (bond) angles as in the normal unit cell. In DD, the second network undergoes a dramatic restructuring-the tetrahedral nodes transform into two new types of mirror-symmetric nodes (pentahedral and trihedral) which alternate and link to form a hexagonal mesh in the plane of the TB. The collective reorganization of the supramolecular packing highlights the hierarchical structure of ordered BCP phases and emphasizes the remarkable malleability of soft matter.

Tensile Deformation Behaviors of Pure Ti with Different Grain Sizes under Wide-Range of Strain Rate

In this study, pure titanium equivalent to Grade 1 was subjected to tensile tests at strain rates ranging from 10^-6 to 10⁰ s^-1 to investigate the relationship between its mechanical properties and its twinning and slip. Deformation properties and microstructures of samples having average grain sizes of 210 μm (Ti-210), 30 μm (Ti-30), and 5 μm (Ti-5) were evaluated. With increasing strain rates, the 0.2% proof stress and ultimate tensile strength increased for all samples; the fracture strain increased for Ti-210, decreased for Ti-5, and changed negligibly for Ti-30. Comparing high (10⁰ s^-1) and low (10^-6 s^-1) strain rates, twinning occurred more frequently in Ti-30 and Ti-210 at high strain rates, but the frequency did not change in Ti-5. The frequency of 1st order pyramidal slip tended to be higher in Ti-30 and Ti-5 at low strain rates. The higher ductility exhibited by Ti-210 at high strain rates was attributed to the high frequency of twinning. In contrast, the higher ductility of Ti-5 at low strain rates was attributed to the activity of the 1st order pyramidal slip.

Stability and change in genetic and environmental influences on depressive symptoms in response to COVID-19 pandemic

BACKGROUND

The rapid spread of the new Coronavirus and the consequent restrictions to contain transmission generated an unprecedented psychological impact on the general population. The Italian Twin Registry performed a longitudinal study to investigate to what extent genetic and environmental influences contributed to changes in depressive symptoms.

METHODS

Data from adult twins were collected. All participants completed an online questionnaire including the 2-item Patient Health Questionnaire (PHQ-2) just before (February 2020) and immediately after the Italian lockdown (June 2020). Genetic modeling based on Cholesky decomposition was used to estimate the role of genetic (A) and both shared (C) and unshared (E) environmental factors in the observed longitudinal course of depressive symptoms.

RESULTS

Longitudinal genetic analysis was based on 348 twin pairs (215 monozygotic and 133 dizygotic pairs) with a mean age of 42.6 years (range 18-93 years). An AE Cholesky model provided heritability estimates for depressive symptoms of 0.24 and 0.35 before and after the lockdown period, respectively. Under the same model, the observed longitudinal trait correlation (0.44) was approximately equally contributed by genetic (46%) and unshared environmental (54%) influences, while longitudinal environmental correlation was lower than genetic correlation (0.34 and 0.71, respectively).

CONCLUSIONS

Although the heritability of depressive symptoms was rather stable across the targeted time window, different environmental as well as genetic factors seemed to act before and after the lockdown, which suggests possible gene-environment interaction.

Prenatal Diagnosis of Structural Anomaly Among Singletons and Twins: Eight-Year Experience in a Chinese Tertiary Center

OBJECTIVES

This study was designed to reveal structural abnormalities in singleton and twin pregnancies in the Chinese population.

METHODS

This retrospective study spanned 8 years and included 1228 singleton pregnancies (112,919 examinees) and 49 twin pregnancies (1865 examinees) with structural anomalies diagnosed by ultrasound. Detailed descriptions of anomalies, gestational weeks at diagnosis, and maternal age were recorded. The odds ratio was evaluated in twin pregnancies with detectable structural anomalies.

RESULTS

The annual average "ultrasound prevalence of fetal anomalies" among singleton and twin pregnancies were 1.09 and 3.06%, respectively. Mothers with twin anomalies were older (P < .001), and twin pregnancies were diagnosed with anomalies in earlier gestational weeks than singleton (P = .011). No differences were found in the types of anomalies between singleton and twin pregnancies. Central nervous system anomaly was the most common type in singleton and twin pregnancies. Twin pregnancies had higher rates of major anomalies than singleton (total OR 2.45), especially cardiovascular, central nervous, and gastrointestinal systems and ear/eye/face/neck disorders.

CONCLUSIONS

Compared with singleton, twin pregnancies had higher odds of detectable structural anomalies. Twin pregnancies with structural anomalies were diagnosed at earlier gestational age and associated with older maternal age. Central nervous system anomaly was the most common type in singleton and twin pregnancies.

Fetoscopic laser surgery for twin-to-twin transfusion syndrome in DCTA triplets compared to MCDA twins: collaborative study and literature review

OBJECTIVE

To compare the outcomes of dichorionic triamniotic (DCTA) triplets with that of monochorionic diamniotic (MCDA) twin gestations undergoing fetoscopic laser surgery (FLS) for treatment of twin-to-twin transfusion syndrome (TTTS).

METHODS

Retrospective cohort study of prospectively collected data of consecutive DCTA triplet and MCDA twin pregnancies with TTTS that underwent FLS at two fetal treatment centers between 2012 and 2020. Preoperative, operative and, postoperative variables were collected. Perinatal outcomes were investigated. Primary outcome was survival to birth and to neonatal period. Secondary outcomes were gestational age (GA) at birth and procedure-to-delivery interval. Literature review was conducted in which PubMed, Web of Science, and Scopus were searched from inception to September, 2020.

RESULTS

Twenty four sets of DCTA triplets were compared to MCDA twins during the study period. There were no significant differences in survival (no survivor, single, or double survivors) to birth and to the neonatal period of the MC twin pairs of the DCTA triplets vs MCDA twins. Median GA at delivery was approximately three weeks earlier in DCTA triplets compared to MCDA twins (28.4 weeks vs 31.4 weeks, p = .035, respectively). Rates of preterm birth (PTB) less than 32 and less than 28 weeks were significantly higher in DCTA triplets compared to twins (<32 weeks: 70.8% vs 51.1%, p = .037, respectively, and <28 weeks: 37.5% vs 20.8%, p = .033, respectively).

CONCLUSION

Perinatal survival including fetal and neonatal are comparable between DCTA triplets and MCDA twins. However, this might have resulted from the small sample size of the DCTA triplets. GA at delivery is earlier in triplets, which could be due to the nature of triplet gestation rather than to the laser procedure itself.

Placenta accreta spectrum disorders in twin pregnancies as an under reported clinical entity: a case series and systematic review

Recent reports suggested a potential association between twin pregnancy and the occurrence of placenta accreta spectrum (PAS) disorders. Despite this, scarce data on PAS disorders in twins has been reported in the published literature. We present a series of twelve twin pregnancies complicated by PAS from two large institutions over 5 years. A systematic review of the literature was also conducted in order to find studies reporting on the risk factors, prenatal diagnosis using ultrasound and clinical outcomes of PAS in twin pregnancies.

Screening Accuracy of the 50 g-Glucose Challenge Test in Twin Compared With Singleton Pregnancies

CONTEXT

The optimal 50 g-glucose challenge test (GCT) cutoff for the diagnosis of gestational diabetes mellitus (GDM) in twin pregnancies is unknown.

OBJECTIVE

This work aimed to explore the screening accuracy of the 50 g-GCT and its correlation with the risk of large for gestational age (LGA) newborn in twin compared to singleton pregnancies. A population-based retrospective cohort study (2007-2017) was conducted in Ontario, Canada. Participants included patients with a singleton (n = 546 892 [98.4%]) or twin (n = 8832 [1.6%]) birth who underwent screening for GDM using the 50 g-GCT.

METHODS

We compared the screening accuracy, risk of GDM, and risk of LGA between twin and singleton pregnancies using various 50 g-GCT cutoffs.

RESULTS

For any given 50 g-GCT result, the probability of GDM was higher (P = .0.007), whereas the probability of LGA was considerably lower in the twin compared with the singleton group, even when a twin-specific growth chart was used to diagnose LGA in the twin group (P < .001). The estimated false-positive rate (FPR) for GDM was higher in twin compared with singleton pregnancies irrespective of the 50 g-GCT cutoff used. The cutoff of 8.2 mmol/L (148 mg/dL) in twin pregnancies was associated with an estimated FPR (10.7%-11.1%) that was similar to the FPR associated with the cutoff of 7.8 mmol/L (140 mg/dL) in singleton pregnancies (10.8%).

CONCLUSION

The screening performance of the 50 g-GCT for GDM and its correlation with LGA differ between twin and singleton pregnancies.

Molecular Characterization of a Rare Case of Monozygotic Dichorionic Diamniotic Twin Pregnancy after Single Blastocyst Transfer in Preimplantation Genetic Testing (PGT)

Preimplantation genetic testing (PGT) is widely used to select unaffected embryos, increasing the odds of having a healthy baby. During the last few decades, it was accepted that monozygotic dichorionic diamniotic twin pregnancies occurred from the embryo splitting before Day 3 postfertilization according to Corner’s dogma. Hence, the occurrence of a dichorionic diamniotic twin pregnancy after a single blastocyst transfer was considered a dizygotic pregnancy resulting from blastocyst transfer and concurrent natural fertilization. In our study, we have provided for the first time molecular proof that a single blastocyst transfer can result in a monozygotic dichorionic diamniotic twin pregnancy, invalidating Corner’s dogma. In this case, we recommend systematically assessing the genetic status of dichorionic twins after single blastocyst transfer using prenatal diagnosis to exclude the risk from a potential concurrent spontaneous pregnancy and to ensure that both fetuses are unaffected. To achieve this goal, we have developed here an innovative noninvasive prenatal diagnosis by exclusion of paternal variants with droplet digital PCR, maximizing the reliability of genetic diagnosis. Further multicentric prospective studies using genetic testing are now required to establish the rate of blastocyst splitting leading to dichorionic pregnancy in PGT and to identify the risk factors.

Differences in Nutritional Intake, Total Body Fat, and BMI Score between Twins

The present study aimed to investigate the coincidence of obesity and nutritional intake in monozygotic twins compared to dizygotic twins. The data from the Korean Genome and Epidemiology Study (KoGES) from 2005 through 2014 were analyzed. Participants ≥ 20 years old were enrolled. The 1006 monozygotic twins and 238 dizygotic twins were analyzed for differences in self-reported nutritional intake, total body fat, and body mass index (BMI) using a linear regression model. The estimated values (EV) with 95% confidence intervals (95% CI) of the difference in dietary intake, total body fat, and BMI score were calculated. The monozygotic twin group and the dizygotic twin group showed similar differences in nutritional intake, DEXA fat, and BMI (all p > 0.05). The differences in nutritional intake of total calories and carbohydrates were lower in the monozygotic twin group than in the dizygotic twin group (all p < 0.05). The differences in total body fat were lower in monozygotic twins than in dizygotic twins (adjusted EV = 2427.86 g, 95% CI = 1777.19−3078.53 and adjusted EV = 1.90%, 95% CI = 1.33−2.46). Monozygotic twins had more similar dietary habits for total calories and carbohydrate intake. Other nutritional factors did not show differential similarity between monozygotic and dizygotic twins. Total body fat was more concordant in monozygotic twins.

Observing Dislocations Transported by Twin Boundaries in Al Thin Film: Unusual Pathways for Dislocation-Twin Boundary Interactions

Twins are generally regarded as obstacles to dislocations in face-centered cubic metals and can modify individual dislocations by locking them in twin boundaries or obliging them to dissociate. Through in situ tensile experiments on Al thin film in a transmission electron microscope, we report a dynamic process of dislocations being transported by twin lamella via periodic twinning and detwinning at the atomic scale. Following this process, a 60° dislocation first transforms into a sessile step of the twin boundary, then migrates under stress as a step and finally reverts back into a 60° dislocation. Our results reveal a novel evolution route of dislocations by a dislocation-twin interaction where the twins act as transport vehicles rather than as obstacles. The potential implications of this mechanism on toughening are also discussed.

Incidence and outcome of prenatal brain abnormality in twin-to-twin transfusion syndrome: systematic review and meta-analysis

OBJECTIVES

To evaluate the incidence of antenatally diagnosed brain injury in twin pregnancy complicated by twin-to-twin transfusion syndrome (TTTS) and to quantify the perinatal mortality, morbidity and long-term neurodevelopmental outcome of these fetuses.

METHODS

MEDLINE, EMBASE, ClinicalTrials.gov and The Cochrane Library databases were searched. Inclusion criteria were studies reporting on brain abnormality diagnosed antenatally in twin pregnancies complicated by TTTS. The primary outcome was the incidence of prenatal brain abnormality. The secondary outcomes were intrauterine demise (IUD), neonatal death, termination of pregnancy (TOP) and long-term morbidity. Outcomes were explored in the population of fetuses with antenatal diagnosis of brain abnormality. Subgroup analysis according to the type of treatment, gestational age, Quintero stage at diagnosis and/or treatment, and cotwin death was planned. Meta-analysis of proportions was used to combine data and pooled proportions and their 95% CI were reported.

RESULTS

Thirteen studies including 1573 cases of TTTS and 88 fetuses with an antenatal diagnosis of brain abnormality were included in the systematic review. The meta-analysis included only studies reporting on brain abnormality in twin pregnancy complicated by TTTS cases and treated with laser surgery. Overall, brain injury occurred in 2.2% (52/2410) of fetuses (eight studies). Brain abnormality was reported in 1.03% and 0.82% of recipients and donors, respectively. The most common type of abnormality was ischemic lesions (30.4% (95% CI, 19.1-43.0%)), followed by destructive lesions (23.9% (95% CI, 13.7-35.9%)), ventriculomegaly (19.9% (95% CI, 10.6-31.3%)) and hemorrhagic lesions (15.3% (95% CI, 7.1-25.8%)). Spontaneous IUD occurred in 13.4% (95% CI, 5.1-24.8%) of fetuses, while TOP was chosen by parents in 53.5% (95% CI, 38.9-67.8%) cases. Neonatal death was reported by only three studies, with an incidence of 15.4% (95% CI, 2.8-35.4%). Finally, only two studies reported on composite morbidity, with an overall rate of the outcome of 20.4% (95% CI, 2.5-49.4%) and rates of 29.7% and 20.4% in the recipient and donor fetuses, respectively. Due to the small numbers, only composite morbidity was analyzed and no information on neonatal intensive care unit admission, respiratory distress syndrome or other long-term outcomes, such as neurodevelopmental delay and cerebral palsy, could be retrieved reliably.

CONCLUSIONS

The overall incidence of antenatally diagnosed fetal brain abnormality in twin pregnancy complicated by TTTS treated with laser surgery is around 2% and is mainly ischemic in nature (30.4%). TOP was chosen by parents in more than half of cases (53.5%). No information could be retrieved on morbidity outcomes, highlighting the urgent need for long-term follow-up studies of these children. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.