Pregnancy Outcome of Monochorionic Twins: Does Amnionicity Matter?

Placental and Umbilical Cord Anomalies Detected by Ultrasound as Clinical Risk Factors of Adverse Perinatal Outcome: Case Series Review of Selected Conditions. Part 2: Umbilical Cord Abnormalities

The aim of this second extended review is to describe the pathogenetic mechanisms underlying umbilical cord (UC) anomalies and their relationship with adverse perinatal outcomes. Review of the literature with case presentations to illustrate the relationship between UC pathologies and adverse perinatal outcomes are also reported. Prenatal ultrasound findings and perinatal care in these cases are presented. Our review confirms the ethiopathogenetic role and involvement of UC pathology in a wide variety of obstetric diseases that may jeopardize fetal well-being. Some of these specific pathologies are strongly associated with a high risk of poor perinatal outcomes.

Maternal and perinatal risks for monozygotic twins conceived following frozen-thawed embryo transfer: a retrospective cohort study

BACKGROUND

The present study aimed to explore the maternal and perinatal risks in cases of monozygotic twins (MZT) following frozen-thawed embryo transfer (FET).

METHODS

All twin births that were conceived following FET from 2007 to 2021 at Shanghai Ninth People's Hospital in Shanghai, China were retrospectively reviewed. The exposure variable was twin type (monozygotic and dizygotic). The primary outcome was the incidence of neonatal death while secondary outcomes included hypertensive disorders of pregnancy, gestational diabetes, intrahepatic cholestasis of pregnancy, placenta previa, placental abruption, preterm premature rupture of the membranes, Cesarean delivery, gestational age, birth weight, weight discordance, stillbirth, birth defects, pneumonia, respiratory distress syndrome, necrotizing enterocolitis, and neonatal jaundice. Analysis of the outcomes was performed using logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs). The causal mediation analysis was conducted. A doubly robust estimation model was used to validate the results. Kaplan-Meier method was used to calculate survival probability. The sensitivity analysis was performed with a propensity score-based patient-matching model.

RESULTS

Of 6101 dizygotic twin (DZT) and 164 MZT births conceived by FET, MZT showed an increased risk of neonatal death based on the multivariate logistic regression models (partially adjusted OR: 4.19; 95% CI, 1.23-10.8; fully adjusted OR: 4.95; 95% CI, 1.41-13.2). Similar results were obtained with the doubly robust estimation. Comparing MZT with DZT, the neonatal survival probability was lower for MZT (P < 0.05). The results were robust in the sensitivity analysis. Females with MZT pregnancies exhibited an elevated risk of preterm premature rupture of the membranes (adjusted OR: 2.42; 95% CI, 1.54-3.70). MZT were also associated with higher odds of preterm birth (prior to 37 weeks) (adjusted OR: 2.31; 95% CI, 1.48-3.67), low birth weight (adjusted OR: 1.92; 95% CI, 1.27-2.93), and small for gestational age (adjusted OR: 2.18; 95% CI, 1.21-3.69) in the fully adjusted analyses. The effect of MZT on neonatal death was partially mediated by preterm birth and low birth weight (P < 0.05).

CONCLUSIONS

This study indicates that MZT conceived by FET are related to an increased risk of neonatal death, emphasizing a potential need for comprehensive antenatal surveillance in these at-risk pregnancies.

Intertwin Membrane Perforation and Umbilical Cord Entanglement after Laser Surgery for Twin-Twin Transfusion Syndrome: Prevalence, Risk Factors, and Outcome

INTRODUCTION

Perforation of the intertwin membrane can occur as a complication of fetoscopic laser surgery for twin-twin transfusion syndrome (TTTS). Data on the occurrence and the risk of subsequent cord entanglement are limited. The objective of this study was to assess the prevalence, risk factors and outcome of intertwin membrane perforation, and cord entanglement after laser surgery for TTTS.

METHODS

In this multicenter retrospective study, we included all TTTS pregnancies treated with laser surgery in two fetal therapy centers, Shanghai (China) and Leiden (the Netherlands) between 2002 and 2020. We evaluated the occurrence of intertwin membrane perforation and cord entanglement after laser, based on routine fortnightly ultrasound examination and investigated the risk factors and the association with adverse short- and long-term outcomes.

RESULTS

Perforation of the intertwin membrane occurred in 118 (16%) of the 761 TTTS pregnancies treated with laser surgery and was followed by cord entanglement in 21% (25/118). Perforation of the intertwin membrane was associated with higher laser power settings, 45.8 Watt versus 42.2 Watt (p = 0.029) and a second fetal surgery procedure 17% versus 6% (p < 0.001). The group with intertwin membrane perforation had a higher rate of caesarean section (77% vs. 31%, p < 0.001) and a lower gestational age at birth (30.7 vs. 33.3 weeks of gestation, p < 0.001) compared to the group with an intact intertwin membrane. Severe cerebral injury occurred more often in the group with intertwin membrane perforation, 9% (17/185) versus 5% (42/930), respectively (p = 0.019). Neurodevelopmental outcome at 2 years of age was similar between the groups with and without perforation of the intertwin membrane and between the subgroups with and without cord entanglement.

CONCLUSION

Perforation of the intertwin membrane after laser occurred in 16% of TTTS cases treated with laser and led to cord entanglement in at least 1 in 5 cases. Intertwin membrane perforation was associated with a lower gestational age at birth and a higher rate of severe cerebral injury in surviving neonates.

Determining chorionicity and amnionicity in twin pregnancies: Pitfalls

Although the accuracy of chorioamnionicity determination in multiple pregnancy is nearly 100%, some pitfalls do exist. These pitfalls may arise from some confusing sonographic appearance or because of certain rare variations of twinning going against the general principles. Pitfalls in chorionicity determination include (1) the disappearance of the twin peak sign with the regression of chorion frondosum and thinning of the intertwin membrane with advancing gestation; (2) fake twin peak sign because of other structures creeping into the intertwin membrane-placental junction; (3) intrauterine septum or synechia being mistaken as a thick intertwin membrane; (4) bipartite placenta in monochorionic twin being misinterpreted as two separate placentas of dichorionic twin; (5) erroneous fetal sex determination in sex chromosome mosaicism, monogenic disorders, and malformed genitalia in one fetus; and (6) rare twinning types such as dizygotic monochorionic twin and sesquizygotic twin. Pitfalls in amnionicity determination are (1) the lack of correlation between the number of yolk sacs and amnionicity and (2) failure to visualize the intertwin membrane because of technical issues.

The mystery of monozygotic twinning II: What can monozygotic twinning tell us about Amyoplasia from a review of the various mechanisms and types of monozygotic twinning?

Monozygotic (MZ) twins ("identical twins") are essentially unique to human beings. Why and how they arise is not known. This article reviews the possible different types of MZ twinning recognized in the previous article on twins and arthrogryposis. There appear to be at least three subgroups of MZ twinning: spontaneous, familial, and those related to artificial reproductive technologies. Each is likely to have different etiologies and different secondary findings. Spontaneous MZ twinning may relate to "overripe ova." Amyoplasia, a specific nongenetic form of arthrogryposis, appears to occur in spontaneous MZ twinning and may be related to twin-twin transfusion.

Outcome of twin pregnancy with two live fetuses at 11-13 weeks' gestation

OBJECTIVES

To report and compare pregnancy outcome in dichorionic (DC), monochorionic diamniotic (MCDA) and monochorionic monoamniotic (MCMA) twin pregnancies with two live fetuses at 11-13 weeks' gestation and to examine the impact of endoscopic laser surgery for severe twin-twin transfusion syndrome (TTTS) and/or selective fetal growth restriction (sFGR) on the outcome of MCDA twins.

METHODS

This was a retrospective analysis of prospectively collected data on twin pregnancies undergoing routine ultrasound examination at 11-13 weeks' gestation between 2002 and 2019. In pregnancies with no major abnormalities, we compared overall survival, fetal loss at < 24 weeks' gestation, perinatal death at ≥ 24 weeks, delivery at < 37 and < 32 weeks, and birth weight < 5^th percentile between DC, MCDA and MCMA twins.

RESULTS

The study population of 6225 twin pregnancies with two live fetuses at 11-13 weeks' gestation with no major abnormalities included 4896 (78.7%) DC, 1274 (20.5%) MCDA and 55 (0.9%) MCMA twins. In DC twins, the rate of loss at < 24 weeks' gestation in all fetuses was 2.3%; this rate was higher in MCDA twins (7.7%; relative risk (RR), 3.258; 95% CI, 2.706-3.923) and more so in MCMA twins (21.8%; RR, 9.289; 95% CI, 6.377-13.530). In DC twins, the rate of perinatal death at ≥ 24 weeks in all twins that were alive at 24 weeks was 1.0%; this rate was higher in MCDA twins (2.5%; RR, 2.456; 95% CI, 1.779-3.389) and more so in MCMA twins (9.3%; RR, 9.130; 95% CI, 4.584-18.184). In DC twins, the rate of preterm birth at < 37 weeks' gestation in pregnancies with at least one liveborn twin was 48.6%; this rate was higher in MCDA twins (88.5%; RR, 1.824; 95% CI, 1.760-1.890) and more so in MCMA twins (100%; RR, 2.060; 95% CI, 2.000-2.121). In DC twins, the rate of preterm birth at < 32 weeks was 7.4%; this rate was higher in MCDA twins (14.2%; RR, 1.920; 95% CI, 1.616-2.281) and more so in MCMA twins (26.8%; RR, 3.637; 95% CI, 2.172-6.089). In DC twin pregnancies with at least one liveborn twin, the rate of a small-for-gestational-age neonate among all liveborn twins was 31.2% and in MCDA twins this rate was higher (37.8%; RR, 1.209; 95% CI, 1.138-1.284); in MCMA twins, the rate was not significantly different (33.3%; RR, 1.067; 95% CI, 0.783-1.455). Kaplan-Meier analysis showed a significant difference in survival in MCDA and MCMA twins, compared to DC twins, for both the interval of 12 to < 24 weeks' gestation (log-rank test, P < 0.0001 for both) and that of ≥ 24 to 38 weeks (log-rank test, P < 0.0001 for both). Endoscopic laser ablation of intertwin communicating placental vessels was carried out in 127 (10.0%) MCDA twin pregnancies for TTTS and/or sFGR and, in 111 of these, surgery was performed at < 24 weeks; both fetuses survived in 62 (55.9%) cases, one fetus survived in 25 (22.5%) cases and there were no survivors in 24 (21.6%) cases. On the extreme assumption that, had laser surgery not been carried out in these cases, all fetuses would have died, the total fetal loss rate at < 24 weeks' gestation in MCDA twins would have been 13.5%.

CONCLUSIONS

The rates of fetal loss at < 24 weeks' gestation, perinatal death at ≥ 24 weeks and preterm birth are higher in MCDA and more so in MCMA twins than in DC twins. In MCDA twins, the rate of fetal loss may have been reduced by endoscopic laser surgery in those that developed early TTTS and/or sFGR. These data would be useful in counseling parents as to the likely outcome of their pregnancy and in defining strategies for surveillance and interventions in the management of the different types of twin pregnancy. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Perinatal mortality, timing of delivery and prenatal management of monoamniotic twin pregnancy: systematic review and meta-analysis

OBJECTIVE

To quantify the rate of perinatal mortality in monochorionic monoamniotic (MCMA) twin pregnancies, according to gestational age, and to ascertain the incidence of mortality in pregnancies managed as inpatients compared with those managed as outpatients.

METHODS

MEDLINE, EMBASE and CINAHL databases were searched for studies on monoamniotic twin pregnancy. The primary outcomes explored were the incidence of intrauterine death (IUD), neonatal death (NND) and perinatal death (PND) in MCMA twins at different gestational-age windows (24-30, 31-32, 33-34, 35-36 and ≥ 37 weeks of gestation). The secondary outcomes were the incidence of IUD, NND and PND in MCMA twins according to the type of fetal monitoring (inpatient vs outpatient), and the incidence of delivery ahead of schedule. Random-effects model meta-analyses were used to analyze the data.

RESULTS

Twenty-five studies (1628 non-anomalous twins reaching 24 weeks of gestation) were included. Single and double intrauterine deaths occurred in 2.5% (95% CI, 1.8-3.3%) and 3.8% (95% CI, 2.5-5.3%) of cases, respectively. IUD occurred in 4.3% (95% CI, 2.8-6.2%) of twins at 24-30 weeks, in 1.0% (95% CI, 0.6-1.7%) at 31-32 weeks and in 2.2% (95% CI, 0.9-3.9%) at 33-34 weeks of gestation, while there was no case of IUD, either single or double, from 35 weeks of gestation. In MCMA twin pregnancies managed mainly as inpatients, the incidence of IUD was 3.0% (95% CI, 1.4-5.2%), while the corresponding figure for those managed mainly as outpatients was 7.4% (95% CI, 4.4-11.1%). Finally, 37.8% (95% CI, 28.0-48.2%) of MCMA pregnancies were delivered before the scheduled time, due mainly to spontaneous preterm labor or abnormal cardiotocographic findings.

CONCLUSIONS

MCMA twins are at high risk of perinatal loss during the third trimester of pregnancy, with the large majority of such losses occurring as apparently unexpected events. Inpatient management seems to be associated with a lower rate of mortality, although further studies are needed in order to establish the appropriate type and timing of prenatal assessment in these pregnancies. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Prognosis of the co-twin following spontaneous single intrauterine fetal death in twin pregnancies: a systematic review and meta-analysis

BACKGROUND

Single intrauterine fetal death affects approximately 6% of twin pregnancies and can have serious sequelae for the surviving co-twin.

OBJECTIVES

Determine the prognosis of the surviving co-twin following spontaneous single intrauterine fetal death to aid counselling patients and highlight future research areas.

SEARCH STRATEGY

Medline, Embase, Web of Science, and Cochrane Library, from 1980 to June 2017.

SELECTION CRITERIA

Studies of five or more cases of spontaneous single intrauterine fetal death after 14 weeks gestation, in diamniotic twin pregnancies.

DATA COLLECTION AND ANALYSIS

Summary event rates were calculated and stratified by chorionicity. Monochorionic and dichorionic twins, and sub-groups, were compared by odds ratios.

MAIN RESULTS

In monochorionic twins, when single intrauterine fetal death occurred at less than 28 weeks' gestation, this significantly increased the rate of co-twin intrauterine fetal death [odds ratio (OR) 2.31, 95% confidence interval (CI) 1.02-5.25, I²  = 0.0%, 12 studies, 184 pregnancies] and neonatal death (OR 2.84, 95% CI 1.18-6.77, I²  = 0.0%, 10 studies, 117 pregnancies) compared with when the single intrauterine fetal death occurred at more than 28 weeks' gestation. Neonatal death in monochorionic twins was significantly higher if the pregnancy was complicated by fetal growth restriction (OR 4.83, 95% CI 1.14-20.47, I²  = 0.0%, six studies, 60 pregnancies) or preterm birth (OR 4.95, 95% CI 1.71-14.30, I²  = 0.0%, 11 studies, 124 pregnancies). Abnormal antenatal brain imaging was reported in 20.0% (95% CI 12.8-31.1, I²  = 21.9%, six studies, 116 pregnancies) of surviving monochorionic co-twins. The studies included in the meta-analysis demonstrated small study effects and possible selection bias.

CONCLUSIONS

Preterm birth was the commonest adverse outcome affecting 58.5 and 53.7% of monochorionic and dichorionic twin pregnancies. Outcomes regarding brain imaging and neurodevelopmental comorbidity are an important area for future research, but meta-analysis may be limited due to different methods of assessment.

TWEETABLE ABSTRACT

Preterm birth is the highest risk in single co-twin death. Abnormal antenatal brain imaging was found in 1/5 surviving MC twins.

Pitfalls in assessing chorioamnionicity: novel observations and literature review

Accurate diagnosis of chorioamnionicity in multiple pregnancies is the key to appropriate clinical management of multiple gestation. Although prenatal ultrasound assessment of chorioamnionicity is well established and highly accurate if performed in early pregnancy, exceptions and artifacts arise from anatomic variations in multiple pregnancies and unusual sonographic features do exist. We have summarized our own experiences and reports from the literature on these pitfalls as follows: (1) discordant fetal sex in monochorionic pregnancies due to sex chromosome abnormalities, genital malformation in 1 fetus, or dizygotic twins forming a monochorionic placenta; (2) separate placental masses in monochorionic pregnancies due to bipartite placenta; (3) false-negative and false-positive λ sign can arise for various reasons, and in partial monochorionic/dichorionic placentas both T and λ sign may co-exist; (4) intrauterine synechia appearing as a thick and echogenic intrauterine septum may lead to erroneous diagnosis of dichorionic twins; and (5) errors in ascertaining amnionicity by the visualization of thin intertwin amniotic membranes and the number of yolk sacs. The ultrasound techniques to reduce inaccuracy in prenatal determination of chorioamnionicity and the use of single nucleotide polymorphisms based on noninvasive prenatal test to determine zygosity are also reviewed.

Intervention versus a conservative approach in the management of TRAP sequence: a systematic review

OBJECTIVE

In the management of twin reversed arterial perfusion (TRAP) sequence, we wished to (i) determine if intervention is better than a conservative approach and (ii) assess if any of the apparent adverse prognostic indicators could guide intervention.

METHODS

A systematic review was conducted between 1994 and 2014. Data extracted were inspected for heterogeneity. Overall rates and confidence intervals (CIs) for each prognostic factor were calculated. Where there were comparative data, the odds ratio (OR) was calculated.

RESULTS

Twenty-six studies were included in the review. When all cases were considered, intervention either by cord occlusion or by ablation conferred a better survival rate compared with conservative management (OR=2.22, 95% CI 1.23-4.01, heterogeneity I2=37%, P=0.008). This difference was greater in the presence of one or more poor prognostic features (OR=8.58, 95% CI 1.47-49.96, heterogeneity I2=0%, P=0.02). Survival was better using ablative techniques compared to cord occlusion (OR=9.84, 95% CI 1.56-62.00, heterogeneity I2=0%, P=0.01).

CONCLUSION

Intervention either by cord occlusion or by ablation confers a better survival rate compared to conservative management. This appears more compelling if there are one or more poor prognostic features. Ablative techniques are superior to cord occlusion. There were insufficient data to determine which poor prognostic features should guide management.

Does antenatal ultrasound labeling predict birth order in twin pregnancies?

OBJECTIVE

It is often assumed by obstetricians, neonatologists and parents that the prenatal nomenclature used to identify twins on ultrasound is consistent with twin labeling after their birth. The aim of this study was to use a large regional database of twin ultrasound scans to validate the effectiveness of a scan before delivery in predicting twin birth-order.

METHODS

A large regional database of twin ultrasound scans with data from nine hospitals over a 10-year period was used to identify all ultrasound examinations carried out just before birth. The discordance in twin order between the last scan and birth was evaluated by observing discrepancies in fetal sex and weight.

RESULTS

In total, 2103 twin pregnancies with ultrasound estimated fetal weights (EFWs) and birth weights were assessed. Of these, fetal sex was recorded in 149 different-sex pregnancies. Discrepancy between antenatal labeling and the anticipated birth order was noted in 37.6% (56/149) of cases when judged by sex discordance and in 36% (757/2103) of cases when judged by weight discordance. Multiple logistic regression analyses demonstrated that weight discordance, but not chorionicity, scan-to-delivery interval, gestation at scan or gestation at delivery, significantly influenced the change in birth order (P < 0.001).

CONCLUSION

Antenatal ultrasound labeling does not predict twin birth-order in a significant proportion of twin deliveries. This finding should be borne in mind not only by parents, but also by physicians when delivering twins discordant for anomalies that are not evident on external examination.