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

Perinatal Outcomes Following Selective Fetal Terminations of Complicated Monochorionic Pregnancies: Experience From a Referral Center in Southern Spain

The objective of this study was to to describe perinatal outcomes in monochorionic twin pregnancies after selective fetal reduction using bipolar cord coagulation (BCC) or interstitial laser ablation (ILA). This retrospective cohort study included monochorionic twin pregnancies requiring selective fetal reduction between 2008 and 2023 at a referral center in Spain. Maternal and perinatal data were collected and analyzed to compare outcomes between BCC and ILA techniques. The primary outcome was the survival of the co-twin, while secondary outcomes included gestational age at delivery, the incidence of PPROM, birth weight and long-term neurodevelopmental outcomes. Eighty-four procedures were performed (30 ILA, 54 BCC). The overall co-twin survival rate was 80%, with BCC showing a higher survival rate (87%) compared to ILA (67%, p = .026). Fetal death before 24 weeks was more common in ILA (30%) than BCC (7.4%, p = .010). The mean gestational age at delivery was lower in BCC (36.6 weeks) than ILA (38.6 weeks, p = .021), and preterm delivery was more frequent in BCC (50%) compared to ILA (14%, p = .005). BCC seems to have a better overall survival than ILA in complicated monochorionic twins' selective terminations. However, we could not clarify whether this difference was due to the technique itself or the different gestational age at the time of the procedure as well as the specific indication.

Diagnostic accuracy of cell-free fetal DNA in maternal blood in detecting chromosomal anomalies in twin pregnancy: systematic review and meta-analysis

OBJECTIVE

To report the diagnostic accuracy of cell-free fetal DNA (cfDNA) in maternal blood in detecting fetal chromosomal anomalies in twin pregnancy.

METHODS

PubMed, MEDLINE, EMBASE and Cochrane databases were searched from inception to November 2023. The inclusion criteria were twin pregnancy undergoing cfDNA screening for trisomies 21, 18 and 13, monosomy X and/or other sex-chromosome aneuploidies (SCA). The index test was cfDNA screening. The reference standard was pre- or postnatal karyotyping (in the case of a positive cfDNA result) or neonatal phenotypic assessment (in case of a negative cfDNA result). The quality of included studies was assessed using the revised quality assessment of diagnostic accuracy studies (QUADAS-2) tool. Summary estimates of diagnostic accuracy were computed using a bivariate random-effects model.

RESULTS

Thirty-five studies were included in the systematic review and meta-analysis. cfDNA had a high accuracy in detecting trisomy 21 in twin pregnancy, with a sensitivity of 98.8% (95% CI, 96.5-100%) and specificity of 100% (95% CI, 99.9-100%). Sensitivity and specificity were 94.9% (95% CI, 75.9-99.1%) and 100% (95% CI, 99.9-100%), respectively, for trisomy 18 and 84.6% (95% CI, 54.6-98.1%) and 100% (95% CI, 99.9-100%), respectively, for trisomy 13. We could not compute the diagnostic accuracy of cfDNA in detecting monosomy X, owing to an absence of positive cases, while cfDNA had a sensitivity of 100% (95% CI, 71.5-100%) and specificity of 99.8% (95% CI, 99.7-99.9%) for other SCA. The accuracy of cfDNA in detecting the common trisomies was similar in dichorionic and monochorionic twin pregnancies.

CONCLUSIONS

cfDNA has high diagnostic accuracy in detecting trisomies 21 and 18 in twin pregnancy, irrespective of chorionicity. Estimation of diagnostic accuracy for trisomy 13 and other SCA was limited by the small number of affected cases and the difficulty associated with detecting false-negative cases of other SCA, and thus requires confirmation in larger studies. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Dichorionic Diamniotic Twin Reduction Surviving the Odds: A Case Report

A 19-year-old woman presented with reduction of twin pregnancy to singleton pregnancy when premature rupture of the membrane of one dichorionic diamniotic twin at eight weeks of gestation led to premature delivery and fetal demise at 19 weeks of gestation. Despite reactive stress tests performed 11 weeks after rupture of membranes, baby A was delivered via spontaneous vaginal delivery and demised without the assistance of uterotonic medications. Although professional options and limited studies suggested a poor outcome for the remaining fetus, extraordinary measures performed led to a successful, full-term singleton pregnancy.

Routine 36-week scan: prediction of small-for-gestational-age neonate

OBJECTIVES

First, to compare the predictive performance of routine ultrasonographic estimated fetal weight (EFW) at 31 + 0 to 33 + 6 and 35 + 0 to 36 + 6 weeks' gestation for delivery of a small-for-gestational-age (SGA) neonate. Second, to compare the predictive performance of EFW at 36 weeks' gestation for SGA vs fetal growth restriction (FGR) at birth. Third, to compare the predictive performance for delivery of a SGA neonate of EFW < 10th percentile vs a model combining maternal demographic characteristics and elements of medical history with EFW.

METHODS

This was a retrospective analysis of prospectively collected data in 21 676 women with a singleton pregnancy who had undergone routine ultrasound examination at 31 + 0 to 33 + 6 weeks' gestation and 107 875 women with a singleton pregnancy who had undergone routine ultrasound examination at 35 + 0 to 36 + 6 weeks. Measurements of fetal head circumference, abdominal circumference and femur length were used to calculate EFW according to the Hadlock formula and this was expressed as a percentile according to the Fetal Medicine Foundation fetal and neonatal population weight charts. The same charts were used to diagnose SGA neonates with birth weight < 10th or < 3rd percentile. FGR was defined as birth weight < 10th percentile in addition to Doppler anomalies. For each gestational-age window at screening, the screen-positive rate and detection rate were calculated at different EFW cut-offs between the 10th and 50th percentiles for predicting the delivery of a SGA neonate with birth weight < 10th or < 3rd percentile, either within 2 weeks or at any time after assessment. The areas under the receiver-operating-characteristics curves (AUC) of screening for a SGA neonate by EFW at 31 + 0 to 33 + 6 weeks and at 35 + 0 to 36 + 6 weeks were compared.

RESULTS

The predictive performance of routine ultrasonographic examination during the third trimester for delivery of a SGA neonate is higher if: first, the scan is carried out at 35 + 0 to 36 + 6 weeks' gestation rather than at 31 + 0 to 33 + 6 weeks; second, the outcome measure is birth weight < 3rd rather than < 10th percentile; third, the outcome measure is FGR rather than SGA; fourth, if delivery occurs within 2 weeks after assessment rather than at any time after assessment; and fifth, prediction is performed using a model that combines maternal demographic characteristics and elements of medical history with EFW rather than EFW < 10th percentile alone. At 35 + 0 to 36 + 6 weeks' gestation, detection of ≥ 85% of SGA neonates with birth weight < 10th percentile born at any time after assessment necessitates the use of EFW < 40th percentile. Screening at this percentile cut-off predicted 95% and 98% of neonates with birth weight < 10th and < 3rd percentile, respectively, born within 2 weeks after assessment, and the respective values for neonates born at any time after assessment were 85% and 93%.

CONCLUSION

Routine third-trimester ultrasonographic screening for a SGA neonate performs best when the scan is carried out at 35 + 0 to 36 + 6 weeks' gestation, rather than at 31 + 0 to 33 + 6 weeks, and when EFW is combined with maternal risk factors to estimate the patient-specific risk. © 2024 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Ultrasound diagnosis of first trimester umbilical cord entanglement in monochorionic monoamniotic twins - case report and review of the literature

BACKGROUND

Diagnosis of umbilical cord entanglement (UCE) by ultrasound (US) in monochorionic monoamniotic (MCMA) twins in the second and third trimesters is common. However, only a few cases have been reported on the diagnosis of UCE as early as the first trimester. Herein, we report a case of the earliest-ever sonographic diagnosis of UCE and demonstrate the feasibility of its diagnosis by US.

CASE PRESENTATION

A 32-year-old gravida 2 para 1 woman conceived after assisted reproductive technology (ART) treatment. In transvaginal US examination at 8.5 gestational weeks, two embryos with regular heartbeats in the same amniotic sac and with only one yolk sac were demonstrated. The fetal crown-rump lengths were 20 and 21 mm, appropriate for 8.4 and 8.5 gestational weeks, respectively. HD-flow power Doppler 2D and 3D US demonstrated two tightly entangled umbilical cords of the two fetuses. Spectral Doppler US showed two different heart rates (162 and 167 beats per minute) and blood flow in opposite directions from the point of entanglement of the two umbilical cords. This was consistent with a diagnosis of a first-trimester MCMA pregnancy with UCE. Missed abortion of the two embryos was diagnosed by US examination at 10.5 weeks, and the pregnancy was terminated by dilatation and curettage without further complications.

CONCLUSIONS

UCE in the first trimester may occur as early as eight gestational weeks, and its diagnosis by ultrasound is feasible. UCE diagnosed in the first trimester may be a poor prognostic factor.

Monochorionic Twin Complications and Fetoscopic Interventions

Monochorionic twins are at risk for complications due to the presence of placental vascular anastomoses, including twin-twin transfusion syndrome, twin anemia-polycythemia sequence, selective fetal growth restriction, and twin reversed arterial perfusion sequence. While ultrasound is the primary modality to screen for the development of these complications, MRI plays an important role in assessing monochorionic twin pregnancies for the development of other complications, such as neurologic injury. In this article, the authors review the ultrasound imaging findings associated with monochorionic twin complications, management options, and the role for MRI in these pregnancies.

First-trimester screening identifies maternal cardiac maladaptation in midgestation

OBJECTIVE

We have previously established that a logistic regression model, based on maternal demographic characteristics and blood pressure measured at 11-13 weeks' gestation, can identify about 70% of women who develop future chronic hypertension (CH) in the 3 years following pregnancy, at a screen-positive rate of 10%. Furthermore, in midgestation, women who subsequently develop hypertensive disorders of pregnancy (HDP) have increased peripheral vascular resistance and mild cardiac functional and morphological alterations and these cardiovascular abnormalities persist for at least 2 years after delivery. In this study, we set out to examine whether use of the first-trimester risk model for subsequent development of CH can help to identify women at high risk for cardiovascular maladaptation in midgestation.

METHODS

This was a prospective observational study of 3812 women with singleton pregnancy attending for a routine hospital visit at 11 + 0 to 13 + 6 weeks' gestation and again at 19 + 1 to 23 + 3 weeks at King's College Hospital, London, UK, between December 2019 and August 2020. The first-trimester visit included recording of maternal demographic characteristics and medical history and measurement of systolic and diastolic blood pressure. In midgestation, detailed maternal cardiovascular assessment was carried out. The association between risk for development of CH, determined from first-trimester assessment, and cardiovascular indices in midgestation was examined.

RESULTS

Women who were at high risk for development of future CH, compared to those at low risk, had a higher incidence of HDP. In addition, high-risk women had reduced systolic and diastolic function in midgestation. Among women with HDP, those who were at high risk for future CH, compared to those at low risk, had worse cardiac function in midgestation.

CONCLUSIONS

Use of a model for first-trimester prediction of subsequent development of CH can identify women who show evidence of cardiac maladaptation in midgestation. Further studies are needed to clarify whether women who screen as high risk for future CH, compared to those at low risk, have reduced cardiac function beyond pregnancy. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

In Vitro Fertilization and Adverse Pregnancy Outcomes in the Elective Single Embryo Transfer Era

OBJECTIVE

Our objective was to estimate the association between in vitro fertilization (IVF) pregnancy and adverse pregnancy outcomes during delivery hospital admission in a contemporary, nation-wide cohort of births in the United States.

STUDY DESIGN

This retrospective, population-based cohort study used the National Inpatient Sample database to identify patients discharged from the hospital following delivery from 2014 to 2019. IVF pregnancies were identified using the International Classification of Disease-Revision 9/10 codes. Crude and adjusted odds ratios of preterm birth and other clinically significant adverse pregnancy outcomes were evaluated using multivariable logistic regression models. Trends in preterm birth and multiple pregnancy were estimated over the study period. The contribution of multiple pregnancy to preterm birth in IVF pregnancy was estimated in a mediation analysis.

RESULTS

Among 4,451,667 delivery-related discharges, IVF pregnancies were associated with 3.25 times the odds of preterm birth (95% confidence interval [CI]: 3.05-3.46, p < 0.001) compared with non-IVF pregnancy deliveries. Odds of preterm birth in IVF pregnancy delivery discharges decreased over the study period (p-value for linear trend = 0.009). The proportion of multiple pregnancies decreased in IVF pregnancy delivery discharges but remained stable in non-IVF pregnancy deliveries. The proportion of the adjusted effect of IVF pregnancy on preterm birth mediated through multiple pregnancy was 67.6% (95% CI: 62.6-72.7%).

CONCLUSION

While the odds of adverse pregnancy outcomes are increased compared with non-IVF pregnancies, the odds of preterm birth and multiple gestation have decreased among IVF pregnancies in the United States.

KEY POINTS

· Pregnancies conceived by in vitro fertilization (IVF) are at significantly higher risk of multiple gestation, preterm birth, and other pregnancy complications.. · Recent guidelines for artificial reproductive treatments recommend single-embryo transfer in IVF.. · Using population-wide data, we demonstrate a significant gradual decline in the rates of preterm birth and other pregnancy complications following IVF in the last decade, mostly mediated by a reduction in multiple pregnancies..

Intra-abdominal umbilical venous diameter and abdominal circumference discordance at 15-20 weeks' gestation: simple markers in transverse abdominal plane to predict adverse pregnancy outcomes in monochorionic diamniotic twins

PURPOSE

This study aimed to investigate the association between simple markers in fetal abdominal plane, intra-abdominal umbilical venous diameter (DIUV) and abdominal circumference (AC) discordance at 15-20 weeks' gestation, and adverse pregnancy outcomes in monochorionic diamniotic (MCDA) twins.

METHODS

We performed a retrospective analysis of MCDA twins with two live fetuses examined at 15-20 weeks from Jun 2020 to Dec 2021 at Beijing Obstetrics and Gynecology Hospital. Measurement of fetal AC and DIUV was performed according to standard protocols. Twin pregnancies with major fetal structural anomalies, chromosomal abnormalities, miscarriage, and twin reversed arterial perfusion sequence were excluded. DIUV and AC discordance in MCDA twins with an adverse pregnancy outcome was compared with a normal pregnancy outcome. Furthermore, the performance of DIUV and AC discordance in predicting adverse pregnancy outcomes in MCDA twins was assessed.

RESULTS

A total of 105 women with MCDA twin pregnancies were enrolled, contributing 179 visits. Adverse pregnancy outcomes occurred in 33.3% (35/105) of cases in our study. The intra-observer and inter-observer intraclass correlation coefficient (ICC) of both AC and DIUV were very good or excellent. There was no statistical difference in AC and DIUV discordance (%) between 15-16, 17-18, and 19-20 weeks (χ2 = 3.928, P = 0.140; χ2 = 2.840, P = 0.242). Both AC and DIUV discordance were greater in twins with adverse pregnancy outcomes than that in twins with normal pregnancy outcome at each pregnancy periods. Both AC discordance (OR 1.2, 95% CI 1.1-1.3) and DIUV discordance (OR 1.2, 95% CI 1.1-1.2) were associated with adverse pregnancy outcomes. The AUC for predicting adverse pregnancy outcomes by AC discordance was 0.75 (95% CI 0.68-0.83), with a sensitivity of 58.7% (95% CI 51.9-64.5) and a specificity of 86.2% (95% CI 81.7-88.4). The AUC for predicting adverse pregnancy outcomes by DIUV was 0.78 (95% CI 0.70-0.86), with sensitivity and specificity of 65.1% (95% CI 58.1-70.3) and 86.2% (95% CI 81.7-88.4), respectively.

CONCLUSIONS

The AC discordance and DIUV discordance could predict adverse pregnancy outcomes in MCDA twins. When these simple markers occurred, intensive surveillance was recommended.

Fetal Medicine Foundation charts for fetal growth in twins

OBJECTIVE

To derive reference distributions of estimated fetal weight (EFW) in twins relative to singletons.

METHODS

Gestational-age- and chorionicity-specific reference distributions for singleton percentiles and EFW were fitted to data on 4391 twin pregnancies with two liveborn fetuses from four European centers, including 3323 dichorionic (DC) and 1068 monochorionic diamniotic (MCDA) twin pregnancies. Gestational age was derived using the larger of the two crown-rump length measurements obtained during the first trimester of pregnancy. EFW was obtained from ultrasound measurements of head circumference, abdominal circumference and femur length using the Hadlock formula. Singleton percentiles were obtained using the Fetal Medicine Foundation population weight charts for singleton pregnancies. Hierarchical models were fitted to singleton Z-scores with autoregressive terms for serial correlations within the same fetus and between twins from the same pregnancy. Separate models were fitted for DC and MCDA twins.

RESULTS

Fetuses from twin pregnancies tended to be smaller than singletons at the earliest gestational ages (16 weeks for MCDA and 20 weeks for DC twins). This was followed by a period of catch-up growth until around 24 weeks. After that, both DC and MCDA twins showed reduced growth. In DC twins, the EFW corresponding to the 50th percentile was at the 50th percentile of singleton pregnancies at 23 weeks, the 43rd percentile at 28 weeks, the 32nd percentile at 32 weeks and the 22nd percentile at 36 weeks. In MCDA twins, the EFW corresponding to the 50th percentile was at the 36th percentile of singleton pregnancies at 24 weeks, the 29th percentile at 28 weeks, the 19th percentile at 32 weeks and the 12th percentile at 36 weeks.

CONCLUSIONS

In DC and, to a greater extent, MCDA twin pregnancies, fetal growth is reduced compared with that observed in singleton pregnancies. Furthermore, after 24 weeks, the divergence in growth trajectories between twin and singleton pregnancies becomes more pronounced as gestational age increases. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Preterm Birth: Screening and Prediction

Preterm birth (PTB) affects approximately 10% of births globally each year and is the most significant direct cause of neonatal death and of long-term disability worldwide. Early identification of women at high risk of PTB is important, given the availability of evidence-based, effective screening modalities, which facilitate decision-making on preventative strategies, particularly transvaginal sonographic cervical length (CL) measurement. There is growing evidence that combining CL with quantitative fetal fibronectin (qfFN) and maternal risk factors in the extensively peer-reviewed and validated QUanititative Innovation in Predicting Preterm birth (QUiPP) application can aid both the triage of patients who present as emergencies with symptoms of preterm labor and high-risk asymptomatic women attending PTB surveillance clinics. The QUiPP app risk of delivery thus supports shared decision-making with patients on the need for increased outpatient surveillance, in-patient treatment for preterm labor or simply reassurance for those unlikely to deliver preterm. Effective triage of patients at preterm gestations is an obstetric clinical priority as correctly timed administration of antenatal corticosteroids will maximise their neonatal benefits. This review explores the predictive capacity of existing predictive tests for PTB in both singleton and multiple pregnancies, including the QUiPP app v.2. and discusses promising new research areas, which aim to predict PTB through cervical stiffness and elastography measurements, metabolomics, extracellular vesicles and artificial intelligence.

Clinical Factors for Predicting Pharmacotherapy in Twin Pregnancies Complicated by Gestational Diabetes Mellitus

Controlling blood glucose levels is the main target in pregnant women with gestational diabetes mellitus (GDM). Twin pregnancies are offered the same screening selection and have the same diagnostic criteria as well as treatment of gestational diabetes as singleton pregnancies, even though the risks for pregnancy complications are increased. The aim of this study was to assess the association between predicting factors, OGTT glucose levels and pharmacotherapy requirements in twin pregnancies with GDM. This retrospective cohort study included 446 GDM patients with twin pregnancies (246 managed with lifestyle modifications and 200 requiring pharmacotherapy) over a time period of 18 years. An evaluation of maternal characteristics and a standardized 75 g oral glucose test (OGGT) for glucose concentrations at fasting, 1 h and 2 h were conduced. OGTT glucose levels at fasting (=0 min, p < 0.01) and 1 h (p < 0.01) were significantly associated with the later requirement of pharmacotherapy. Also, clinical risk factors (pre-pregnancy BMI p < 0.01, multiparity p < 0.05, GDM in previous pregnancy p < 0.01, assisted reproduction p < 0.05) showed a predictive accuracy for insulin therapy in twin pregnancies complicated by GDM, whereas age and chorionicity had no effect. OGTT glucose measures in addition to clinical risk factors are promising variables for risk stratification in mothers with GDM and twin pregnancy.

Cervical cerclage for prevention of preterm birth and adverse perinatal outcome in twin pregnancies with short cervical length or cervical dilatation: A systematic review and meta-analysis

BACKGROUND

The optimal approach to prevent preterm birth (PTB) in twins has not been fully established yet. Recent evidence suggests that placement of cervical cerclage in twin pregnancies with short cervical length at ultrasound or cervical dilatation at physical examination might be associated with a reduced risk of PTB. However, such evidence is based mainly on small studies thus questioning the robustness of these findings. The aim of this systematic review was to determine the role of cervical cerclage in preventing PTB and adverse maternal or perinatal outcomes in twin pregnancies.

METHODS AND FINDINGS

Key databases searched and date of last search: MEDLINE, Embase, and CINAHL were searched electronically on 20 April 2023. Eligibility criteria: Inclusion criteria were observational studies assessing the risk of PTB among twin pregnancies undergoing cerclage versus no cerclage and randomized trials in which twin pregnancies were allocated to cerclage for the prevention of PTB or to a control group (e.g., placebo or treatment as usual). The primary outcome was PTB <34 weeks of gestation. The secondary outcomes were PTB <37, 32, 28, 24 weeks of gestation, gestational age at birth, the interval between diagnosis and birth, preterm prelabor rupture of the membranes (pPROM), chorioamnionitis, perinatal loss, and perinatal morbidity. Subgroup analyses according to the indication for cerclage (short cervical length or cervical dilatation) were also performed. Risk of bias assessment: The risk of bias of the included randomized controlled trials (RCTs) was assessed using the Revised Cochrane risk-of-bias tool for randomized trials, while that of the observational studies using the Newcastle-Ottawa scale (NOS). Statistical analysis: Summary risk ratios (RRs) of the likelihood of detecting each categorical outcome in exposed versus unexposed women, and (b) summary mean differences (MDs) between exposed and unexposed women (for each continuous outcome), with their 95% confidence intervals (CIs) were computed using head-to-head meta-analyses. Synthesis of the results: Eighteen studies (1,465 twin pregnancies) were included. Placement of cervical cerclage in women with a twin pregnancy with a short cervix at ultrasound or cervical dilatation at physical examination was associated with a reduced risk of PTB <34 weeks of gestation (RR: 0.73, 95% CI [0.59, 0.91], p = 0.005 corresponding to a 16% difference in the absolute risk, AR), <32 (RR: 0.69, 95% CI [0.57, 0.84], p < 0.001; AR: 16.92%), <28 (RR: 0.54, 95% [CI 0.43, 0.67], 0.001; AR: 18.29%), and <24 (RR: 0.48, 95% CI [0.23, 0.97], p = 0.04; AR: 15.57%) weeks of gestation and a prolonged gestational age at birth (MD: 2.32 weeks, 95% [CI 0.99, 3.66], p < 0.001). Cerclage in twin pregnancy with short cervical length or cervical dilatation was also associated with a reduced risk of perinatal loss (RR: 0.38, 95% CI [0.25, 0.60], p < 0.001; AR: 19.62%) and composite adverse outcome (RR: 0.69, 95% CI [0.53, 0.90], p = 0.007; AR: 11.75%). Cervical cerclage was associated with a reduced risk of PTB <34 weeks both in women with cervical length <15 mm (RR: 0.74, 95% CI [0.58, 0.95], p = 0.02; AR: 29.17%) and in those with cervical dilatation (RR: 0.68, 95% CI [0.57, 0.80], p < 0.001; AR: 35.02%). The association between cerclage and prevention of PTB and adverse perinatal outcomes was exclusively due to the inclusion of observational studies. The quality of retrieved evidence at GRADE assessment was low.

CONCLUSIONS

Emergency cerclage for cervical dilation or short cervical length <15 mm may be potentially associated with a reduction in PTB and improved perinatal outcomes. However, these findings are mainly based upon observational studies and require confirmation in large and adequately powered RCTs.

Directive clinique no 440 : Prise en charge de la grossesse gémellaire monochoriale

OBJECTIF

Cette directive clinique passe en revue les données probantes sur la prise en charge de la grossesse gémellaire monochoriale normale et compliquée.

POPULATION CIBLE

Les femmes menant une grossesse gémellaire ou multiple de haut rang. BéNéFICES, RISQUES ET COûTS: L'application des recommandations de cette directive devrait améliorer la prise en charge des grossesses gémellaires (ou multiples de haut rang) monochoriales compliquées et non compliquées. Ces recommandations aideront les fournisseurs de soins à surveiller adéquatement les grossesses gémellaires monochoriales ainsi qu'à détecter et prendre en charge rapidement les complications associées de façon optimale afin de réduire les risques de morbidité et mortalité périnatales. Ces recommandations impliquent une surveillance échographique plus fréquente en cas de grossesse monochoriale qu'en cas de grossesse bichoriale. DONNéES PROBANTES: La littérature publiée a été colligée par des recherches dans les bases de données PubMed et Cochrane Library au moyen de termes MeSH pertinents (Twins, Monozygotic; Ultrasonography, Prenatal; Placenta; Fetofetal Transfusion; Fetal Death; Fetal Growth Retardation). Les résultats ont été restreints aux revues systématiques, aux essais cliniques randomisés et aux études observationnelles. Aucune date limite n'a été appliquée, mais les résultats ont été limités aux contenus en anglais ou en français. MéTHODES DE VALIDATION: Les auteurs principaux ont rédigé le contenu et les recommandations et ils se sont entendus sur ces derniers. Le conseil d'administration de la SOGC a approuvé la version définitive aux fins de publication. Les auteurs ont évalué la qualité des données probantes et la force des recommandations en utilisant le cadre méthodologique GRADE (Grading of Recommendations Assessment, Development and Evaluation). Voir l'annexe A en ligne (tableau A1 pour les définitions et tableau A2 pour l'interprétation des recommandations fortes et conditionnelles [faibles]). PROFESSIONNELS CONCERNéS: Spécialistes en médecine fœto-maternelle, obstétriciens, radiologues, échographistes, médecins de famille, infirmières, sages-femmes, résidents et autres fournisseurs de soins de santé qui s'occupent de femmes menant une grossesse gémellaire ou multiple de haut rang. RéSUMé POUR TWITTER: Directive canadienne (SOGC) pour le diagnostic, la surveillance échographique et la prise en charge des complications de la grossesse gémellaire monochoriale (p. ex., STT, TAPS, retard de croissance sélectif, cojumeau acardiaque, monoamnionicité et mort d'un jumeau). DÉCLARATIONS SOMMAIRES: RECOMMANDATIONS.

Guideline No. 440: Management of Monochorionic Twin Pregnancies

OBJECTIVE

This guideline reviews the evidence-based management of normal and complicated monochorionic twin pregnancies.

TARGET POPULATION

Women with monochorionic twin or higher order multiple pregnancies.

BENEFITS, HARMS, AND COSTS

Implementation of these recommendations should improve the management of both complicated and uncomplicated monochorionic (and higher order multiple) twin pregnancies. They will help users monitor monochorionic twin pregnancies appropriately and identify and manage monochorionic twin complications optimally in a timely manner, thereby reducing perinatal morbidity and mortality. These recommendations entail more frequent ultrasound monitoring of monochorionic twins compared to dichorionic twins.

EVIDENCE

Published literature was retrieved through searches of PubMed and the Cochrane Library using appropriate MeSH headings (Twins, Monozygotic; Ultrasonography, Prenatal; Placenta; Fetofetal Transfusion; Fetal Death; Fetal Growth Retardation). Results were restricted to systematic reviews, randomized controlled clinical trials, and observational studies. There were no date limits, but results were limited to English or French language materials.

VALIDATION METHODS

The content and recommendations were drafted and agreed upon by the principal authors. The Board of the SOGC approved the final draft for publication. The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional [weak] recommendations).

INTENDED AUDIENCE

Maternal-fetal medicine specialists, obstetricians, radiologists, sonographers, family physicians, nurses, midwives, residents, and other health care providers who care for women with monochorionic twin or higher order multiple pregnancies.

TWEETABLE ABSTRACT

Canadian (SOGC) guidelines for the diagnosis, ultrasound surveillance and management of monochorionic twin pregnancy complications, including TTTS, TAPS, sFGR (sIUGR), acardiac (TRAP), monoamniotic twins and intrauterine death of one MC twin.

SUMMARY STATEMENTS

RECOMMENDATIONS.

The High-Risk Profile of Selective Growth Restriction in Monochorionic Twin Pregnancies

The present review aims to provide a critical appraisal of the sonographic diagnosis and follow-up and to evaluate the optimal clinical management of monochorionic twin pregnancies where one of the twins is complicated by selective fetal growth restriction (sFGR). The classification is based on the umbilical artery (UA) diastolic flow reflecting the outcome. If the sFGR twin has positive diastolic flow (Type I) then the prognosis is good, and it does not require close surveillance. Biweekly or weekly sonographic and Doppler surveillance and fetal monitoring are recommended strategies to detect unpredictable complications in type II and type III forms, which are defined by persistently absent/reverse end-diastolic flow (AREDF) or cyclically intermittent absent/reverse end-diastolic flow (iAREDF) in the umbilical waveforms, respectively. The latest forms are associated with an increased risk of unexpected fetal demise of the smaller twin and 10-20% risk of neurological injury in the larger twin in addition to the overall risk of prematurity. The clinical course can be affected by elective fetal therapy ('dichorinization' of the placenta with laser or selective fetal reduction) or elective delivery in the presence of severe fetal deterioration. The prediction of the clinical outcome in complicated cases of type II and III sFGR cases remains elusive. Novel routines in fetal and placental scans in order to predict neurological impairments and unexpected fetal death to optimize the delivery time-point are needed.

Perioperative risk factors of preterm delivery after fetoscopic laser photocoagulation for twin-twin transfusion syndrome

OBJECTIVE

To identify risk factors for preterm delivery (PTD) in patients who received fetoscopic laser photocoagulation (FLP) of placental anastomoses for twin-twin transfusion syndrome (TTTS).

METHODS

This retrospective cohort study prospectively analyzed and recorded perioperative data in a cohort of patients who had FLP for TTTS, identifying perioperative risk factors for PTD using a Cox proportional hazard regression model.

RESULTS

Of 304 patients included, 26 (8.6%) delivered within 4 weeks of FLP. Independent predictors of delivery within 4 weeks of FLP were a history of PTD (hazard ratio [HR]: 5.91, 95% confidence interval [CI]:1.21-28.82, p = 0.03), vaginal bleeding in the second trimester (HR: 6.62, 95% CI: 1.76-24.90, p < 0.01), and amnioreduction ≥1715 mL (HR: 3.16, 95% CI: 1.11-9.05, p < 0.03).

CONCLUSION

Patients with a history of PTD, preoperative vaginal bleeding, and amnioreduction ≥1715 mL were more likely to deliver prematurely.

Serum hsCRP in early pregnancy and preterm delivery in twin gestations: a prospective cohort study

BACKGROUND

Systemic inflammation during pregnancy may be associated with preterm delivery (PTD), but data for twin gestations are lacking. The aim of this study was to examine the association of serum high-sensitivity C-reactive protein (hsCRP), a marker of inflammation, in early pregnancy of twin gestations with risk of PTD, including spontaneous (sPTD) and medical-induced preterm delivery (mPTD).

METHODS

A prospective cohort study involved 618 twin gestations was conducted in a tertiary hospital in Beijing, from 2017 to 2020. Serum samples collected in early pregnancy were analyzed for hsCRP using particle-enhanced immunoturbidimetric method. Unadjusted and adjusted geometric means (GM) of hsCRP were estimated using linear regression, and compared between PTD before 37 weeks of gestation and term delivery at 37 or more weeks of gestation using Mann-Whitney rank sum test. The association between hsCRP tertiles and PTDs was estimated using logistic regression, and further converted overestimated odds ratios into relative risks (RR).

RESULTS

A total of 302 (48.87%) women were classified as PTD, with 166 sPTD and 136 mPTD. The adjusted GM of serum hsCRP was higher in PTDs (2.13 mg/L, 95% confidence interval [CI] 2.09 -2.16) compared to term deliveries (1.84 mg/L, 95% CI 1.80 -1.88) (P < 0.001). Compared with the lowest tertile of hsCRP, the highest tertile was associated with increased risk of PTD (adjusted relative risks [ARR] 1.42; 95% CI: 1.08-1.78). Among twin pregnancies, the adjusted association between high values of serum hsCRP in early pregnancy and preterm delivery was only observed in the subgroup of spontaneous preterm deliveries (ARR 1.49, 95%CI:1.08-1.93).

CONCLUSIONS

Elevated hsCRP in early pregnancy was associated with increased risk of PTD, particular the risk of sPTD in twin gestations.

Fetal oxygen and glucose utilization of uncomplicated monochorionic twins: Adapting to the intrauterine environment

INTRODUCTION

Monochorionic twins (MC) develop under unique intrauterine conditions and show a high risk of compromise during fetal life. Here we describe umbilical vein blood flow (UVBF) and fetal oxygen and glucose utilization in uncomplicated MC twins and investigate possible differences within twin-pairs according to birth-order.

METHODS

Prospective single-center study on 48 uncomplicated MC twins enrolled at the time of elective cesarean delivery. Ultrasound measurements of UVBF for Twin 1 and Twin 2 labelled according to birth-order were performed before spinal anesthesia. Umbilical arterial and venous blood samples were collected for each twin after fetal delivery, and fetal oxygen and glucose deliveries and uptakes were computed.

RESULTS

All twins were delivered within 2 min from one-another under steady-state conditions at 36.4 weeks of median gestational age (IQR 36.0-37.0). Birthweight and umbilical cord gas analyses were within physiological ranges for all twins. Second-born twins showed significantly lower UVBF, measured before delivery, and lower median birthweight compared to first-borns. Moreover, median values of estimated fetal oxygen and glucose consumption were lower in second compared to first MC twins.

DISCUSSION

Uncomplicated MC twins show different birthweight, oxygenation and metabolic rates based on their position in utero, hinting at pre-existing conditions possibly deriving by uneven vascular and metabolic distribution of the two placental territories. The innovative findings of this study emphasize the biological uniqueness of these pregnancies and prompt further physiological studies on MC twins and placenta metabolism.

Are there differences between monochorionic twin placentas after spontaneous and assisted conception?

INTRODUCTION

No data are available on the placental characteristics of monochorionic twin pregnancies conceived by in vitro fertilization (IVF). This study investigates the differences between placentas from monochorionic diamniotic (MCDA) twin pregnancies conceived spontaneously and those conceived after IVF.

METHODS

This is a retrospective analysis of placental data from a consecutive series of MCDA twin pregnancies followed from the first trimester. The following placental characteristics were compared between IVF versus spontaneous MCDA pregnancies: placental sharing and birth weight discordance relative to placental sharing, the placental angioarchitecture (number, type, and size of anastomoses), and the umbilical cord insertion types.

RESULTS

Of the 256 MCDA placentas included in this analysis, 32 (12%) were conceived through IVF and 224 (88%) spontaneously. MCDA twin placentas after IVF did not differ significantly from MCDA twin placentas after spontaneous conception regarding placental sharing, birthweight discordance relative to sharing discordance, and angioarchitecture. There was a trend toward more discordant cord insertions (combination eccentric and velamentous) in IVF (25%) than in spontaneously conceived placentas (12%) (P = 0.05).

DISCUSSION

No differences could be demonstrated between MCDA placentation after spontaneous conception and IVF. Any differences in pregnancy outcome between spontaneous and IVF conceived MCDA twins may not be related to differences in placental sharing, angioarchitecture and cord insertion type.

Association between fetal sex and pregnancy outcomes among women with twin pregnancies: a multicenter cross-sectional study

PURPOSE

To examine the frequency and to what extent fetal sex is associated with pregnancy outcomes among twin pregnancies, stratified by chorionicity.

METHODS

This registry-based multicenter cross-sectional study was conducted using the Japan Society of Obstetrics and Gynecology perinatal database between 2007 and 2016. The sample population was restricted to women with twin pregnancies. The main pregnancy-related outcomes included preterm birth, very preterm birth, extremely preterm birth, preeclampsia, twin-to-twin transfusion syndrome (TTTS), and selective intrauterine growth restriction (s-IUGR). Birth weight, small for gestational age (SGA), and fetal death were also investigated.

RESULTS

The primary analysis was performed based on 37,953 women, including 23,804 women with dichorionic diamniotic (DD) twins and 14,149 women with monochorionic diamniotic (MD) twins. Women with male/male DD twins had a significantly higher risk of preterm birth (adjusted risk ratio [aRR]: 1.07, 95% confidence interval [CI]: 1.03-1.10) and a lower risk of preeclampsia (aRR: 0.74, 95% CI: 0.62-0.88) than women with female/female DD twins. Women with male/male MD twins also had a significantly higher risk of preterm birth (aRR: 1.06, 95% CI: 1.04-1.09) than women with female/female MD twins. Risks of preeclampsia, TTTS, and s-IUGR did not differ by sex among MD pregnancies. Male SGA risk was significantly higher among male/male twins than among male/female DD twins. Among MD twins, risks of SGA and fetal death were significantly higher in male/male fetuses.

CONCLUSIONS

This study demonstrated significant associations between fetal sex and several pregnancy outcomes in twin pregnancies, some of which differed by chorionicity.

Amniocentesis in Twin Pregnancies: Risk Factors of Fetal Loss

This study aims to determine if second trimester amniocentesis in twin pregnancies provides a significant independent contribution in the prediction of miscarriage or fetal loss at any stage of pregnancy. This was a retrospective cohort study of women with twin gestations booked for routine prenatal care in four fetal medicine units in Poland in the years 2010-2020. The study population included: (1) twin pregnancies that underwent amniocentesis at 16-20 weeks' gestation; (2) twin pregnancies that did not require any further testing and were followed-up routinely. Univariable and multivariable regression analysis was used to define which maternal and pregnancy characteristics provided a significant independent contribution in the prediction of miscarriage and fetal loss at any stage of pregnancy. In the study period, 2645 twin pregnancies were eligible for analysis. There were 144 cases of miscarriage defined as fetal loss of one or both twins before 24 weeks and 40 cases of intrauterine death of one or both twins after 24 weeks. A total number of 162 twin pregnancies underwent amniocentesis at 16-20 weeks' gestation. The rate of miscarriage before 24 weeks and the rate of fetal loss at any stage of pregnancy in the group that underwent amniocentesis was 10.49% and 13.58%, respectively, compared to 5.11% and 6.52% that did not undergo amniocentesis. Multivariable regression analysis showed that factors providing a significant independent contribution in the prediction of miscarriage and fetal loss at any stage of pregnancy were monochorionicity (MC), large intertwin discordance in crown-rump length (CRL), low Pregnancy Related Plasma Protein (PAPP-A) MoM and nuchal translucency (NT) above 95th centile. Amniocentesis in twin pregnancies does not provide a significant contribution in the prediction of miscarriage or fetal loss at any stage of pregnancy.

What fetal medicine specialists should know about the monochorionic placenta

Monochorionic twins are at risk of transfusion imbalances as long as they are connected to the shared placenta during their intrauterine journey. This review article addresses the macroscopic examination of the monochorionic placenta at the time of birth and explains placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in twin-twin transfusion syndrome, twin anemia polycythemia sequence and selective fetal growth restriction.

Risk of fetal loss after chorionic villus sampling in twin pregnancy derived from propensity score matching analysis

OBJECTIVE

To estimate the risk of fetal loss associated with chorionic villus sampling (CVS) in twin pregnancy, using propensity score analysis.

METHODS

This was a multicenter cohort study of women with twin pregnancy undergoing ultrasound examination at 11-13 weeks' gestation, performed in eight fetal medicine units in which the leadership were trained at the Harris Birthright Research Centre for Fetal Medicine in London, UK, and in which the protocols for screening, invasive testing and pregnancy management are similar. The risk of death of at least one fetus was compared between pregnancies that had and those that did not have CVS, after propensity score matching (1:1 ratio). This procedure created two comparable groups by balancing the maternal and pregnancy characteristics that lead to CVS being performed, similar to how randomization operates in a randomized clinical trial.

RESULTS

The study population of 8581 twin pregnancies included 445 that had CVS. Death of one or two fetuses at any stage during pregnancy occurred in 11.5% (51/445) of pregnancies in the CVS group and in 6.3% (515/8136) in the non-CVS group (P < 0.001). The propensity score algorithm matched 258 cases that had CVS with 258 non-CVS cases; there was at least one fetal loss in 29 (11.2%) cases in the CVS group and in 35 (13.6%) cases in the matched non-CVS group (odds ratio (OR), 0.81; 95% CI, 0.48-1.35; P = 0.415). However, there was a significant interaction between the risk of fetal loss after CVS and the background risk of fetal loss; when the background risk was higher, the risk of fetal loss after CVS decreased (OR, 0.46; 95% CI, 0.23-0.90), while, in pregnancies with a lower background risk of fetal loss, the risk of fetal loss after CVS increased (OR, 2.45; 95% CI, 0.95-7.13). The effects were statistically significantly different (P-value of the interaction = 0.005). For a pregnancy in which the background risk of fetal loss was about 6% (the same as in our non-CVS population), there was no change in the risk of fetal loss after CVS, but, when the background risk was more than 6%, the posterior risk was paradoxically reduced, and when the background risk was less than 6%, the posterior risk increased exponentially; for example, if the background risk of fetal loss was 2.0%, the relative risk was 2.8 and the posterior risk was 5.6%.

CONCLUSION

In twin pregnancy, after accounting for the risk factors that lead to both CVS and spontaneous fetal loss and confining the analysis to pregnancies at lower prior risk, CVS seems to increase the risk of fetal loss by about 3.5% above the patient's background risk. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

The association between vein-to-vein anastomoses and birth weight discordance in relation to placental sharing in monochorionic twin placentas

INTRODUCTION

This study aims to examine the association between the presence and size of a vein-to-vein (VV) anastomosis and birth weight discordance relative to placental discordance in monochorionic diamniotic twin pregnancies.

METHODS

Placentas of two previous prospective studies were included in this retrospective analysis. After injection with color dye, we measured the placental surface of each twin and VV, artery-to-artery (AA), and artery-to-vein (AV) anastomoses on a digital photograph. We calculated the birth weight ratio (BWR), placental ratio (PR), and birth weight ratio/placenta ratio (BWR/PR), as well as total AV size and net AV transfusion. Placental characteristics were compared between placentas with and without VV anastomoses. We performed univariate analyses to assess the following predictors for BWR/PR: VV size, AA size, total AV size, and net AV transfusion. Multivariate analysis was then performed, including the variables significant in univariate analysis.

RESULTS

We analyzed 247 placentas: 58 (23%) with VV anastomoses and 189 without (77%). The BWR and PR were higher in the group with VV. In contrast, BWR/PR was lower in the group with VV anastomoses than in those without. The size of AA anastomoses was larger in placentas with VV anastomoses than in those without. In univariate analysis, VV size and AA size were significantly associated with BWR/PR. However, in multivariate regression, only VV size remained significantly associated with the BWR/PR.

DISCUSSION

VV anastomoses are associated with a decreased birth weight discordance relative to the placental sharing discordance, independent of the AA anastomoses.

Multifetal Gestations and Associated Perinatal Risks

Along with the rise of assisted reproductive technology, multifetal gestations increased dramatically. Twin pregnancies account for 97% of multifetal pregnancies and 3% of all births in the United States. Twins and higher-order multiples carry increased risks of obstetric, perinatal, and maternal complications; these risks increase with increasing fetal number. Neonatal morbidity and mortality in multifetal gestations is driven primarily by prematurity. Both spontaneous and indicated preterm births are increased in multifetal gestations, and only a limited number of strategies are available to mitigate this risk. No single intervention has been shown to decrease the rate of spontaneous preterm birth in most twin pregnancies. Low-dose aspirin prophylaxis is recommended in all multifetal pregnancies to reduce the risk of preeclampsia and its associated complications. Antenatal management of multifetal gestations depends on chorionicity, which should be established using ultrasonography in the first trimester. Unlike dichorionic twin gestations, monochorionic pregnancies experience unique complications because of their shared vascular connections, and therefore, need frequent ultrasound surveillance. Even uncomplicated twin gestations have higher rates of unanticipated stillbirth compared with singletons. Delivery of twin pregnancies is generally indicated in the late preterm to early term period depending on chorionicity and other clinical factors. For most diamniotic twin pregnancies with a cephalic presenting fetus, vaginal delivery after 32 weeks' gestation is a safe and reasonable option with high rates of success and no increased risk of perinatal morbidity.

Monochorionic monoamniotic twin pregnancies

Monoamniotic twin pregnancies are rare, but early diagnosis of such pregnancies is critical, as the incidence of complications in these pregnancies is much higher than in diamniotic or dichorionic twin pregnancies. Overall, only 70% of all monoamniotic twins will survive. Furthermore, approximately half of fetal deaths in these pregnancies are because of the high incidence of fetal anomalies (15%-25%), such as twin reversed arterial perfusion sequence and conjoined twinning. Therefore, early anatomy screening in the first trimester of pregnancy is recommended. Other causes of fetal death in these pregnancies include twin-twin transfusion syndrome, tight cord entanglement, or acute hemodynamic imbalances through the large placental vascular anastomoses. After viability, fetal surveillance can be intensified, as this decreases the risk of in utero death. Both inpatient and outpatient surveillance are reasonable. If otherwise uncomplicated, monoamniotic twins should be delivered at 33 to 34 weeks' gestation. Most centers will deliver by cesarean delivery, but some continue to advocate for vaginal delivery. Lastly, neonatal morbidity is high in monoamniotic twin pregnancies and is mainly related to prematurity.

First-Trimester Screening for Gestational Diabetes Mellitus in Twin Pregnancies

We previously reported a logistic regression model for prediction of GDM from maternal characteristics and medical history in 75,161 singleton pregnancies. In this study of 1376 twin and 13,760 singleton pregnancies recruited at 11-13 weeks' gestation, we extend the model to include terms for twin pregnancies. We found the respective odds of GDM in dichorionic and monochorionic twin pregnancies to be 1.36 (95% CI: 1.02-1.81) and 2.78 (95% CI: 1.72-4.48) times higher than in singleton pregnancies. In both singleton and twin pregnancies, the risk for GDM increased with maternal age and weight and birth weight z-score of a baby in a previous pregnancy and is higher in women with a previous pregnancy complicated by GDM; in those with a first- or second-degree relative with diabetes mellitus; in women of Black, East Asian, and South Asian racial origin; and in pregnancies conceived through the use of ovulation-induction drugs. In singleton pregnancies, at 10% and 20% false-positive rate, the detection rate was 43% and 58%, respectively. In twin pregnancies, using risk cut-offs corresponding to 10% and 20% false-positive rates in singletons, the respective false-positive rates were 27% and 47%, and the detection rates were 63% and 81%.

Committee Opinion No. 418: The Complete 11-14 Week Prenatal Sonographic Examination

OBJECTIVE

Sonography during the first trimester provides an opportunity to assess a pregnancy in its early stage. This document provides an opinion about the implementation and content of prenatal sonographic examinations at 11-14 weeks gestation in Canada.

TARGET POPULATION

Pregnant women at 11-14 weeks gestation.

BENEFITS, HARMS, AND COSTS

The 11-14 week prenatal sonographic examination can provide important information that may contribute to pregnancy management. It can be used to confirm viability, establish gestational age, determine the number of fetuses, assess the adnexa/ovaries, and, in a multiple pregnancy, assess chorionicity and amnionicity. Scanning also offers an opportunity to detect fetal abnormalities and perform aneuploidy screening by measuring the nuchal translucency thickness. It may be valuable in screening for preeclampsia and other obstetrical disorders (by combining uterine artery Doppler scanning with other bio-clinical markers) and for invasive placentation. There are no physical harms to mother or fetus from offering a routine 11-14 week prenatal sonographic examination, and there are no extra costs for patients.

EVIDENCE

Articles related to routine 11-14 week prenatal sonography were identified in a search of EMBASE and MEDLINE using the search terms first trimester ultrasound, nuchal translucency, and 11-14 week ultrasound. The search included all articles published on the topic until May 2019. Abstracts were reviewed by one author, and articles deemed relevant were then reviewed in full to determine whether to include them in the study. Articles that were not in English and articles that did not pertain to 11-14 week prenatal sonography were excluded.

INTENDED AUDIENCE

This document is intended for sonographers, midwives, family physicians, obstetricians, and maternal-fetal medicine specialists.

Cell-free DNA testing of maternal blood in screening for trisomies in twin pregnancy: updated cohort study at 10-14 weeks and meta-analysis

OBJECTIVE

To expand the limited knowledge on cell-free DNA (cfDNA) analysis of maternal blood for trisomies 21, 18 and 13 in twin pregnancy by updating the data from The Fetal Medicine Foundation (FMF) on prospective first-trimester screening and those identified in a systematic review of the literature.

METHODS

The FMF data were derived from prospective screening for trisomies 21, 18 and 13 in twin pregnancies at 10 + 0 to 14 + 1 weeks' gestation using the Harmony® prenatal test. A search of MEDLINE, EMBASE, CENTRAL (The Cochrane Library), ClinicalTrials.gov and the International Clinical Trials Registry Platform (World Health Organization) was carried out to identify all peer-reviewed publications on clinical validation or implementation of maternal cfDNA testing for trisomies 21, 18 and 13 in twin pregnancy, irrespective of gestational age at testing, in which data on pregnancy outcome were provided for at least 85% of the study population. Meta-analysis was performed using the FMF data and data from the studies identified by the literature search. This review was registered in the PROSPERO international database for systematic reviews RESULTS: In the FMF study, cfDNA testing was carried out in 1442 twin pregnancies and a result was obtained, after first or second sampling, in 1367 (94.8%) cases. In 93.1% (1272/1367) of cases, there was prenatal or postnatal karyotyping or birth of phenotypically normal babies; 95 cases were excluded from further analysis either because the pregnancy ended in termination, miscarriage or stillbirth with no known karyotype (n = 56) or there was loss to follow-up (n = 39). In the 1272 pregnancies included in the study, there were 20 cases with trisomy 21, 10 with trisomy 18, two with trisomy 13 and 1240 without trisomy 21, 18 or 13. The cfDNA test classified correctly 19 (95.0%) of the 20 cases of trisomy 21, nine (90.0%) of the 10 cases of trisomy 18, one (50.0%) of the two cases of trisomy 13 and 1235 (99.6%) of the 1240 cases without any of the three trisomies. The literature search identified 12 relevant studies, excluding our papers because their data are included in the current study. In the combined populations of our study and the 12 studies identified by the literature search, there were 137 trisomy-21 and 7507 non-trisomy-21 twin pregnancies; the pooled weighted detection rate (DR) and false-positive rate (FPR) were 99.0% (95% CI, 92.0-99.9%) and 0.02% (95% CI, 0.001-0.43%), respectively. In the combined total of 50 cases of trisomy 18 and 6840 non-trisomy-18 pregnancies, the pooled weighted DR and FPR were 92.8% (95% CI, 77.6-98.0%) and 0.01% (95% CI, 0.00-0.44%), respectively. In the combined total of 11 cases of trisomy 13 and 6290 non-trisomy-13 pregnancies, the pooled weighted DR and FPR were 94.7% (95% CI, 9.14-99.97%) and 0.10% (95% CI, 0.03-0.39%), respectively.

CONCLUSIONS

In twin pregnancy, the reported DR of trisomy 21 by cfDNA testing is high, but lower than that in singleton pregnancy, whereas the FPR appears to be equally low. The number of cases of trisomy 18 and more so trisomy 13 was too small for accurate assessment of the predictive performance of the cfDNA test. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Fetal loss after chorionic villus sampling in twin pregnancy

OBJECTIVE

To estimate the chorionic villus sampling (CVS)-related risk of fetal loss in twin pregnancy after adjustment for chorionicity, nuchal translucency thickness (NT), intertwin discordance in crown-rump length (CRL), maternal demographic characteristics and serum pregnancy-associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotropin (β-hCG).

METHODS

This was a multicenter study from eight fetal medicine units in which the leadership were trained at the Harris Birthright Research Centre for Fetal Medicine in London, UK, and in which the protocols for screening, invasive testing and pregnancy management are similar. Data were obtained prospectively from women with twin pregnancy undergoing routine ultrasound examination at 11-13 weeks' gestation. Multivariable logistic regression analysis with backward stepwise elimination was used to examine whether CVS provided a significant independent contribution to the prediction of risk of fetal loss after adjusting for maternal and pregnancy characteristics, including maternal age, racial origin and weight, method of conception, smoking status, parity, chorionicity, intertwin discordance in CRL, fetal NT ≥ 95^th percentile and free β-hCG and PAPP-A multiples of the median. Similarly, within the CVS group, multivariable logistic regression analysis was used to investigate the effect of the number of intrauterine needle insertions and size of the needle on the risk of fetal loss.

RESULTS

The study population of 8581 twin pregnancies undergoing ultrasound examination at 11-13 weeks' gestation included 316 dichorionic and 129 monochorionic twins that had CVS. First, in twin pregnancies undergoing CVS, compared to those not undergoing CVS, there was a 2-fold increased risk of fetal loss at < 24 weeks' gestation and of loss at any stage in pregnancy. Second, the factors providing a significant independent contribution to the prediction of miscarriage or fetal loss in twin pregnancy were increased maternal weight, black racial origin, monochorionicity, and more so monoamnionicity, large intertwin discordance in CRL and increased fetal NT, and, in the case of fetal loss at any stage, there was also a contribution from assisted conception and low serum PAPP-A. Third, after adjustment for maternal and pregnancy characteristics, CVS did not provide a significant contribution to the risk of fetal loss. Fourth, in twin pregnancies that had CVS, there was no significant contribution to fetal loss from the number of intrauterine needle insertions or needle size.

CONCLUSION

The 2-fold increased risk of fetal loss following CVS in twin pregnancy can, to a great extent, be explained by maternal and pregnancy characteristics rather than the invasive procedure itself. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Evaluation of the risk of umbilical cord prolapse in the second twin during vaginal delivery: a retrospective cohort study

OBJECTIVE

This study aimed to evaluate the success rate of vaginal delivery, the reasons for unplanned caesarean delivery, the rate of umbilical cord prolapse and the risk of umbilical cord prolapse in twin deliveries.

DESIGN

Retrospective cohort study.

SETTING

Single institution.

PARTICIPANTS

This study included 455 women pregnant with twins (307 dichorionic and 148 monochorionic) who attempted vaginal delivery from January 2009 to August 2018. The following criteria were considered for vaginal delivery: diamniotic twins, cephalic presentation of the first twin, no history of uterine scar, no other indications for caesarean delivery, no major structural abnormality in either twin and no fetal aneuploidy.

RESULTS

The rate of vaginal delivery of both twins was 89.5% (407 of 455), caesarean delivery of both twins was 7.7% (35 of 455) and caesarean delivery of only the second twin was 2.9% (13 of 455). The major reasons for unplanned caesarean delivery were arrest of labour and non-reassuring fetal heart rate pattern. The rate of umbilical cord prolapse in the second twin was 1.8% (8 of 455). Multivariate analysis revealed that abnormal umbilical cord insertion in the second twin (velamentous or marginal) was the only significant factor for umbilical cord prolapse in the second twin (OR, 5.05, 95% CI 1.139 to 22.472, p=0.033).

CONCLUSIONS

Abnormal umbilical cord insertion in the second twin (velamentous or marginal) was a significant factor for umbilical cord prolapse during delivery. Antenatal assessment of the second twin's umbilical cord insertion using ultrasonography would be beneficial.

Prospective risk of stillbirth and neonatal complications for monochorionic diamniotic and dichorionic diamniotic twins after 24 weeks of gestation

INTRODUCTION

Our study compared the prospective risks of intrauterine fetal death (IUFD), neonatal death (NND), perinatal death (PND), and neonatal morbidities in monochorionic diamniotic (MCDA) and dichorionic diamniotic (DCDA) twin pregnancies.

METHODS

This retrospective cohort study included twin pregnancies who had antenatal care and delivery in a public hospital from 2011 to 2018. Exclusion criteria included monoamnionicity, one/both twin miscarriage, twin-twin transfusion syndrome, or lethal congenital abnormalities. All twins were managed in multiple pregnancy clinic with standardized protocols. Gestational age-specific IUFD, NND, PND, and neonatal morbidity rates were compared according to chorionicity.

RESULTS

Three hundred seventy-eight MCDA and 1282 DCDA twins were included. MCDA twins had higher risks of PND (1.9% vs. 0.7% in DCDA twins, p = 0.05), composite neonatal morbidity (p = 0.01), preterm delivery (p < 0.01), and low birth weight (p < 0.01). The prospective risk of IUFD was 0.6% and 0.4% for MCDA and DCDA twins, respectively after 34 weeks' gestation. No NND occurred among deliveries after 30 weeks. The risk of neonatal morbidity of MCDA twins fell from 22.7% at 34 weeks to 2.7% at 37 weeks (p < 0.01). For DCDA twins, the risk of morbidity fell insignificantly from 36 to 38 weeks (4.0% vs. 3.4%, p = 0.60). Logistic regression analysis suggested that the increased risk of perinatal morbidities was related to the higher rate of preterm delivery in MCDA twins rather than chorionicity.

CONCLUSION

With close fetal monitoring, the risk of late IUFD in twin pregnancies without major complications is low. Perinatal morbidity can be minimized by avoiding late preterm deliveries in twin pregnancies.

Elective Fetal Reduction in Dichorionic Diamniotic Twin Pregnancies on Parental Request: A Single-Centre Experience

OBJECTIVES

Our study aimed to examine a subset of electively reduced twins and compare their outcomes with those of expectantly managed twins, along with a cohort of singleton pregnancies. The secondary aim was to ascertain the procedure-related miscarriage risks.

METHODS

A retrospective cohort analysis was performed at Apollo Centre for Fetal Medicine, New Delhi, comparing pregnancy outcomes in dichorionic diamniotic twin pregnancies which were reduced to singletons (group 1) with that of women with dichorionic twins managed expectantly (group 0) and women with a singleton pregnancy (group 2). Comparison of continuous and categorical variables was conducted using standard statistical tests.

RESULTS

We analysed 35 twins which were reduced to singletons, 421 expectantly managed dichorionic twins and 1915 women with a singleton pregnancy. In the reduction group, the rate of procedure related pregnancy loss<24 weeks was lower, compared to the expectantly managed twins, although the difference was not statistically significant (5.71% [2/35] vs. 7.13% [30/421]; p = 1.000). The median gestational age at delivery was significantly higher in reduced twins compared to expectantly managed twin pregnancies (38.0 vs. 35.4 weeks respectively, p < 0.001) with a higher mean birth weight at delivery, both of which were comparable to that among the singleton pregnancies (38.3 weeks). The rates of preterm birth <32 weeks and <34 weeks in the expectantly managed twins were significantly higher at 19.8% (66/334) and 25.7% (86/334) compared to the reduced twins, all of whom delivered beyond 34 weeks. The rates of preterm births <32 weeks, <34 weeks, and the late preterm births in the reduced twins were comparable to those in the singleton cohort.

CONCLUSIONS

The obstetric and perinatal outcomes after reduction of a dichorionic twin are better than an expectantly managed twin without an associated increase in pregnancy loss rates. Fetal reduction of dichorionic twin to a singleton appears to be a safe procedure in expert hands.

Early Ultrasound Identification of Cord Entanglement in Monochorionic Monoamniotic Twin Pregnancy

Monochorionic monoamniotic pregnancy are considered high risk gestations and the fetal outcome is at times unpredictable. Correct diagnosis and counselling are extremely important, especially regarding the risk of unexpected fetal demise. We present the rare case of a monochorionic monoamniotic twin pregnancy with early identification of cord entanglement and the characteristic ultrasound findings in the first trimester of pregnancy.

Perinatal outcomes and offspring growth profiles in twin pregnancies complicated by gestational diabetes mellitus: A longitudinal cohort study

AIMS

To evaluate the influence of gestational diabetes mellitus (GDM) on the perinatal outcomes of twin pregnancies and its impact on fetal growth profiles of twin offspring from 6 weeks to 12 months of corrected age.

METHODS

A longitudinal cohort study was conducted among pregnant women with twins and their twin offspring. All information on perinatal outcomes and child growth trajectories from 6 weeks to 12 months of corrected age were obtained and analyzed using a general linear model and logistic regression models.

RESULTS

GDM was not correlated with adverse perinatal outcomes of twin pregnancies; however, in monochorionic diamniotic (MCDA), but not dichorionic diamniotic (DCDA) twin pregnancies, GDM was correlated with gestational hypertension disorder and a fetus being small for gestational age (OR, 2.68; 95% CI 1.16-6.04 and OR, 0.35; 95% CI 0.16-0.76, respectively). In both MCDA and DCDA groups, GDM was positively associated with a higher risk of childhood overweight at 6 months of corrected age (2.32 [1.05, 5.09] and 2.00 [1.13, 3.53]).

CONCLUSIONS

GDM had a greater impact on MCDA twin pregnancies in terms of maternal gestational hypertension disease and small for gestational age of newborns. Additionally, twin offspring exposed to GDM had a higher risk of being overweight at 6 months of corrected age irrespective of chorionicity.

CLINICAL TRIAL REGISTRATION

ChiCTR-OOC-16008203.

Risk of fetal loss following amniocentesis or chorionic villus sampling in twin pregnancy: systematic review and meta-analysis

OBJECTIVE

To assess the rate of fetal loss following amniocentesis or chorionic villus sampling (CVS) in twin pregnancy.

METHODS

MEDLINE, EMBASE and Cochrane databases were searched for studies reporting procedure-related complications following amniocentesis or CVS in twin pregnancy. The primary outcome was the rate of procedure-related fetal loss. The secondary outcomes were fetal loss occurring before 24 weeks of gestation and fetal loss occurring within 4 weeks after the procedure. Head-to-head meta-analyses were used to compare directly each outcome, between women undergoing amniocentesis and those not undergoing amniocentesis and between women undergoing CVS and those not undergoing CVS, and to compute pooled risk differences (RD) between women exposed and those not exposed to each invasive procedure. Additionally, meta-analyses of proportions were used to estimate the pooled rates of each of the three outcomes in women undergoing amniocentesis or CVS and in controls.

RESULTS

Sixteen studies (3419 twin pregnancies undergoing and 2517 not undergoing an invasive procedure) were included. Head-to-head meta-analyses comparing directly twin pregnancies undergoing and those not undergoing amniocentesis showed a higher risk for overall fetal loss in those undergoing amniocentesis (odds ratio (OR), 1.46 (P = 0.04); RD, 0.013 (P = 0.04)), while there was no difference in the risk of either fetal loss before 24 weeks of gestation (OR, 1.59 (P = 0.06); RD, 0.010 (P = 0.11)) or fetal loss within 4 weeks after the procedure (OR, 1.38 (P = 0.3); RD, 0.003 (P = 0.8)). Overall, the pooled rate of fetal loss was 2.4% (95% CI, 1.4-3.6%) in twin pregnancies undergoing amniocentesis compared with 2.4% (95% CI, 0.9-4.6%) in those not undergoing amniocentesis. Head-to-head meta-analyses directly comparing twin pregnancies undergoing and those not undergoing CVS showed no significant difference in either overall fetal loss (OR, 1.61 (P = 0.5); RD, 0.003 (P = 0.8)) or fetal loss before 24 weeks of gestation (OR, 1.61 (P = 0.5); RD, 0.003 (P = 0.8)). Overall, the pooled rate of fetal loss was 2.0% (95% CI, 0.0-6.5%) in twin pregnancies undergoing CVS compared with 1.8% (95% CI, 0.3-4.2%) in those not undergoing CVS.

CONCLUSION

The risk of fetal loss following amniocentesis and CVS in twins is lower than reported previously and the rate of fetal loss before 24 weeks of gestation, or within 4 weeks after the procedure, did not differ from the background risk in twin pregnancy not undergoing invasive prenatal testing. These data can guide prenatal counseling for twin pregnancies undergoing invasive procedures. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

The incidence, maternal, fetal and neonatal consequences of single intrauterine fetal death in monochorionic twins: A prospective observational UKOSS study

Objective

Report maternal, fetal and neonatal complications associated with single intrauterine fetal death (sIUFD) in monochorionic twin pregnancies.

Design

Prospective observational study.

Setting

UK.

Population

81 monochorionic twin pregnancies with sIUFD after 14 weeks gestation, irrespective of cause.

Methods

UKOSS reporters submitted data collection forms using data from hospital records.

Main outcome measures

Aetiology of sIUFD; surviving co-twin outcomes: perinatal mortality, central nervous system (CNS) imaging, gestation and mode of delivery, neonatal outcomes; post-mortem findings; maternal outcomes.

Results

The commonest aetiology was twin-twin transfusion syndrome (38/81, 47%), “spontaneous” sIUFD (22/81, 27%) was second commonest. Death of the co-twin was common (10/70, 14%). Preterm birth (<37 weeks gestation) was the commonest adverse outcome (77%): half were spontaneous and half iatrogenic. Only 46/75 (61%) cases had antenatal CNS imaging, of which 33 cases had known results of which 7/33 (21%) had radiological findings suggestive of neurological damage. Postnatal CNS imaging revealed an additional 7 babies with CNS abnormalities, all born at <36 weeks, including all 4 babies exhibiting abnormal CNS signs. Major maternal morbidity was relatively common, with 6% requiring ITU admission, all related to infection.

Conclusions

Monochorionic twin pregnancies with single IUD are complex and require specialist care. Further research is required regarding optimal gestation at delivery of the surviving co-twin, preterm birth prevention, and classifying the cause of death in twin pregnancies. Awareness of the importance of CNS imaging, and follow-up, needs improvement.

The Association Between Hypertension in Pregnancy and Preterm Birth with Fetal Growth Restriction in Singleton and Twin Pregnancy: Use of Twin Versus Singleton Charts

OBJECTIVE

To compare the rates of fetal growth restriction (FGR) in singleton and twin pregnancies using singleton and twin-specific birthweight standards.

METHODS

The study included liveborn twin and singleton pregnancies between January 2000 and January 2019. Hypertensive disorders of pregnancy (HDP) included gestational hypertension and pre-eclampsia. The study outcomes were FGR or small-for-gestational-age (SGA) at birth as assessed using singleton and twin reference charts.

RESULTS

The analysis included 1473 twin and 62,432 singleton pregnancies. In singleton pregnancies the risk of PTB <34 weeks without HDP (OR 2.82, p < 0.001), delivery ≥34 weeks with HDP (OR 2.38, p < 0.001), and PTB <34 weeks with HDP (OR 13.65, p < 0.001) were significantly higher in the pregnancies complicated by FGR compared to those without. When selective fetal growth restriction (sFGR) was assessed using the singleton standard, the risk of PTB <34 weeks without HDP (OR 1.03, p = 0.872), delivery ≥34 weeks with HDP (OR 1.36, p = 0.160) were similar in the pregnancies complicated by sFGR compared to those without, while the risk of PTB <34 weeks with HDP (OR 2.41, p = 0.025) was significantly higher in the pregnancies complicated by sFGR compared to those without. When sFGR was assessed using the twin-specific chart, the risk of PTB <34 weeks without HDP (OR 3.55, p < 0.001), delivery ≥34 weeks with HDP (OR 3.17, p = 0.004), and PTB <34 weeks with HDP (OR 5.69, p < 0.001) were significantly higher in the pregnancies complicated by sFGR compared to those without. The stronger and more consistent association persisted in the subgroup analyses according to chorionicity. The strength of association in dichorionic twin pregnancies resembles that of the singletons more closely and consistently when the FGR was diagnosed using the twin-specific charts.

CONCLUSION

FGR in twin pregnancies has a stronger and more consistent association with HDP and PTB when using twin-specific rather than singleton charts. This study provides further evidence supporting the use of twin-specific charts when assessing fetal growth in twin pregnancies.

Monochorionic diamniotic twins: What do I tell the prospective parents?

Monochorionic diamniotic twins occur in about 1 in 300 pregnancies. Compared with dichorionic twins, they face increased risks because of the shared circulation. In about 15%, an imbalance in blood exchange occurs, such as twin-twin transfusion syndrome and twin anemia polycythemia sequence. In this review, we summarize the latest evidence on the management of monochorionic diamniotic twin pregnancies and their specific complications, with a focus on information that is relevant for prospective parents.

Twin pregnancy with two live fetuses at 11-13 weeks: effect of one fetal death on pregnancy outcome

OBJECTIVES

First, to compare the incidence of single and double fetal death between monochorionic (MC) and dichorionic (DC) twin pregnancies with two live fetuses at 11-13 weeks' gestation and no major abnormalities. Second, to investigate the relationship between gestational age at single fetal death and interval to delivery of the cotwin. Third, to determine the rate of early preterm birth in DC and MC twin pregnancies with two live fetuses and those with single fetal death.

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. The outcome measures, which were stratified by chorionicity, were: first, death of both fetuses at presentation or death of one fetus followed by delivery of a live or dead cotwin within the subsequent 3 days at < 34 weeks' gestation; second, in pregnancies with single fetal death at < 34 weeks' gestation and a live cotwin ≥ 3 days later, the subsequent risk of fetal death and gestational-age distribution at birth of the cotwin; and, third, the gestational-age distribution at birth in pregnancies with two live fetuses.

RESULTS

The main findings of this study of 4896 DC and 1329 MC twin pregnancies with two live fetuses at 11-13 weeks' gestation were: first, the rate of death of both twins or death of one fetus and delivery of the live or dead cotwin within 3 days was higher in MC than in DC twin pregnancies; second, the rate of single fetal death with a live cotwin ≥ 3 days later was higher in MC than in DC twin pregnancies, but the rate of subsequent cotwin death in MC twin pregnancies was not significantly different from that in DC twin pregnancies; third, in pregnancies with two live fetuses, the rate of early preterm birth was significantly higher in MC than in DC twin pregnancies; fourth, the rate of early preterm birth in pregnancies with single fetal death and a live cotwin ≥ 3 days later was not significantly different between MC and DC twin pregnancies but the rates were substantially higher than in those with two live fetuses; and, fifth, in both MC and DC pregnancies with single fetal death and a live cotwin ≥ 3 days later, there was a significant inverse association between gestational age at death and interval to delivery (mean interval of 19 weeks for death at 15 weeks and mean interval of 2.5 weeks for death at 30 weeks).

CONCLUSIONS

First, in MC twin pregnancies, the risk of single or double fetal death is higher than in DC twins. Second, in both MC and DC twin pregnancies, the rate of early preterm birth is higher in those with one fetal death than in those with two live fetuses. Third, in both MC and DC twins with one fetal death, the interval to delivery is related inversely to gestational age at fetal death. These data should be useful in counseling parents as to the likely outcome of their pregnancy after single fetal death and in defining strategies for surveillance in the management of these types of twin pregnancy. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Increased nuchal translucency at 11-13 weeks' gestation and outcome in twin pregnancy

OBJECTIVE

To investigate the value of increased fetal nuchal translucency thickness (NT) at the 11-13-week scan in the prediction of adverse outcome in dichorionic (DC), monochorionic diamniotic (MCDA) and monochorionic monoamniotic (MCMA) twin pregnancies.

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 defects or chromosomal abnormalities, we examined the value of increased NT ≥ 95^th percentile in one or both fetuses in the prediction of, first, miscarriage or death of one or both fetuses at < 20 and < 24 weeks' gestation in DC, MCDA and MCMA twin pregnancies, second, death of one or both fetuses or neonates at ≥ 24 weeks in DC, MCDA and MCMA twin pregnancies, third, development of twin-twin transfusion syndrome (TTTS) or selective fetal growth restriction (sFGR) treated by endoscopic laser surgery at < 20 and ≥ 20 weeks' gestation in MCDA pregnancies, and, fourth, either fetal loss or laser surgery at < 20 weeks' gestation in MCDA pregnancies.

RESULTS

The study population of 6225 twin pregnancies included 4896 (78.7%) DC, 1274 (20.5%) MCDA and 55 (0.9%) MCMA pregnancies. The incidence of NT ≥ 95^th percentile in one or both fetuses in DC twin pregnancies was 8.3%; in MCDA twins the incidence was significantly higher (10.4%; P = 0.016), but in MCMA twins it was not significantly different (9.1%; P = 0.804) from that in DC twins. In DC twin pregnancies, the incidence of high NT was not significantly different between those with two survivors and those with adverse outcome. In MCMA twin pregnancies, the number of cases was too small for meaningful assessment of the relationship between high NT and adverse outcome. In MCDA twin pregnancies with at least one fetal death or need for endoscopic laser surgery at < 20 weeks' gestation, the incidence of NT ≥ 95^th percentile was significantly higher than in those with two survivors (23.5% vs 9.8%; P < 0.0001). Kaplan-Meier analysis in MCDA twin pregnancies showed that, in those with NT ≥ 95^th percentile, there was significantly lower survival at < 20 weeks' gestation than in those with NT < 95^th percentile (P = 0.001); this was not the case for survival at ≥ 20 weeks (P = 0.960). The performance of screening by fetal NT ≥ 95^th percentile for prediction of either fetal loss or need for endoscopic laser surgery at < 20 weeks' gestation was poor, with a detection rate of 23.5% at a false-positive rate of 8.9%, and the relative risk, in comparison to fetal NT < 95^th percentile, was 2.640 (95% CI, 1.854-3.758; P < 0.0001). In MCDA twin pregnancies, the overall rate of fetal loss or need for laser surgery at < 20 weeks' gestation was 10.7% but, in the subgroups with NT ≥ 95^th and NT ≥ 99^th percentiles, which constituted 10.4% and 3.3% of the total, the rates increased to 24.1% and 40.5%, respectively.

CONCLUSIONS

In MCDA twin pregnancies with no major fetal abnormalities, measurement of NT at the 11-13-week scan is a poor screening test for adverse pregnancy outcome. However, the finding in one or both fetuses of NT ≥ 95^th percentile, and more so ≥ 99^th percentile, is associated with a substantially increased risk of fetal loss or need for endoscopic laser surgery at < 20 weeks' gestation. The extent to which closer monitoring and earlier intervention in the high-risk group can reduce these complications remains to be determined. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Intertwin discordance in fetal size at 11-13 weeks' gestation and pregnancy outcome

OBJECTIVE

To investigate the value of intertwin discordance in fetal crown-rump length (CRL) at the 11-13-week scan in the prediction of adverse outcome in dichorionic (DC), monochorionic diamniotic (MCDA) and monochorionic monoamniotic (MCMA) twin pregnancies.

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 examined the value of intertwin discordance in fetal CRL in DC, MCDA and MCMA twins in the prediction of fetal loss at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm delivery at < 32 and < 37 weeks, birth of at least one small-for-gestational-age (SGA) neonate with birth weight < 5^th percentile and intertwin birth-weight discordance of ≥ 20% and ≥ 25%.

RESULTS

First, the study population of 6225 twin pregnancies included 4896 (78.7%) DC, 1274 (20.4%) MCDA and 55 (0.9%) MCMA twin pregnancies. Second, median CRL discordance in DC twin pregnancies (3.2%; interquartile range (IQR), 1.4-5.8%) was lower than in MCDA twins (3.6%; IQR, 1.6-6.2%; P = 0.0008), but was not significantly different from that in MCMA twins (2.9%; IQR, 1.2-5.1%; P = 0.269). Third, compared to CRL discordance in DC twin pregnancies with two non-SGA live births at ≥ 37 weeks' gestation, there was significantly larger CRL discordance in both DC and MCDA twin pregnancies complicated by fetal death at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm birth at < 32 and < 37 weeks, birth of at least one SGA neonate and birth-weight discordance ≥ 20% and ≥ 25%, and in MCDA twin pregnancies undergoing endoscopic laser surgery. Fourth, the predictive performance of CRL discordance for each adverse pregnancy outcome was poor, with areas under the receiver-operating-characteristics curves ranging from 0.533 to 0.624. However, in both DC and MCDA twin pregnancies with large CRL discordance, there was a high risk of fetal loss. Fifth, in DC twin pregnancies, the overall rate of fetal loss at < 20 weeks' gestation was 1.3% but, in the small subgroup with CRL discordance of ≥ 15%, which constituted 1.9% of the total, the rate increased to 5.3%. Sixth, in MCDA twin pregnancies, the rate of fetal loss or endoscopic laser surgery at < 20 weeks was about 11%, but, in the small subgroups with CRL discordance of ≥ 10%, ≥ 15% and ≥ 20%, which constituted 9%, < 3% and < 1% of the total, the risk was increased to about 32%, 49% and 70%, respectively. Seventh, in MCMA twin pregnancies, there were no significant differences in CRL discordance for any of the adverse outcome measures, but this may be the consequence of the small number of cases in the study population.

CONCLUSIONS

In both DC and MCDA twin pregnancies, increased CRL discordance is associated with an increased risk of fetal death at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm birth at < 37 and < 32 weeks, birth of at least one SGA neonate and birth-weight discordance ≥ 20% and ≥ 25%, but CRL discordance is a poor screening test for adverse pregnancy outcome. However, in DC twins, CRL discordance of ≥ 15% is associated with an increased risk of fetal loss at < 20 and < 24 weeks' gestation and, in MCDA twins, CRL discordance of ≥ 10%, and more so discordance of ≥ 15% and ≥ 20%, is associated with a very high risk of fetal loss or endoscopic laser surgery at < 20 and < 24 weeks and this information is useful in counseling women and defining the timing for subsequent assessment and possible intervention. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.