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

The Impact of Dating Twin Pregnancy by the Larger, Smaller or Mean Twin Crown-Rump Length: A Retrospective Cohort Study

OBJECTIVE

To evaluate the impact of twin dating by ultrasound-measured crown-rump length (CRL) of the larger (CRL-L), smaller (CRL-S) or mean twin measurement (CRL-M) on the rates of preterm birth (PTB) and detection of small for gestational age (SGA) births.

DESIGN

A retrospective cohort study.

SETTING

A tertiary fetal medicine centre (London, UK).

POPULATION OR SAMPLE

All twin pregnancies between 1998 and 2023 who underwent first trimester CRL ultrasound assessment and fetal growth assessment.

METHODS

Data collection included CRL measurement, estimated fetal weight (EFW), pregnancy outcome and birthweight (BW) for each twin. Pregnancies were retrospectively re-dated by CRL-S, CRL-L and CRL-M.

MAIN OUTCOME MEASURES

SGA < 10th centile and extreme PTB rates (< 28 weeks).

RESULTS

In the 1129 twin pregnancies, median CRL-S was 61 mm (interquartile range [IQR]: 56.0-66.0) and CRL-L was 63 mm (IQR: 58.4-68.9) with a mean discordance of 4.0%. Prenatal SGA diagnosis occurred in 19.8% and 23.1% of smaller twins when dated by CRL-S and CRL-L, respectively. When pregnancies were dated by CRL-M versus CRL-S or CRL-L, there was no difference in prenatal SGA diagnosis (p = 0.275 and p = 0.419); SGA at birth (p = 0.132 and p = 0.325); or extreme PTB (p = > 0.999 and p = 0.765 respectively).

CONCLUSIONS

Dating by the smaller, larger or mean twin CRL does not significantly alter rates of extreme preterm birth, SGA detection or SGA birth. Dating by the mean twin CRL reduces stigmatisation of the smaller twin and retains the utility of accurate gestational age assessment without impacting clinical outcomes.

The value of ultrasound indicators in early pregnancy for predicting selective intrauterine growth restriction and twin-twin transfusion syndrome: a case‒control study

BACKGROUND

Selective intrauterine foetal growth restriction (sIUGR) and twin-twin transfusion syndrome (TTTS) are common complications in Monochorionic diamniotic (MCDA) twin pregnancies. Timely and accurate diagnosis and intervention are essential to improve perinatal outcomes. The purpose of this study was to determine the value of differences in crown - rump lengths (CRL) and nuchal translucency (NT) and evaluate the significance of differences in embryo length in predicting the occurrence of sIUGR and TTTS.

METHODS

This research is a retrospective study that includes cases of MCDA twins diagnosed via ultrasound in the Obstetrics Department of Shandong Provincial Hospital Affiliated to Shandong University from January 2017 to March 2024. These cases were categorized into sIUGR group, TTTS group, TTTS with sIUGR group and normal MCDA group, based on the presence of complex twin related complications. For each group, embryo length, CRL and NT measured by ultrasound during the 7-14 week gestation period were respectively recorded. The differences in embryo length, CRL and NT between the normal MCDA twin group and sIUGR group, TTTS group, as well as TTTS with sIUGR group were compared. The Mann‒Whitney U test and the chi‒square test were utilized for the analysis. Furthermore, the receiver operating characteristic (ROC) curve was plotted to conduct further analysis.

RESULTS

A total of 722 MCDA twins (203 with sIUGR, 158 with TTTS, 55 with TTTS with sIUGR and 306 controls) were included. The difference in the CRL in the sIUGR group (9.43%) was significantly greater than that in the control group (3.30%) (P < 0.001). However, no statistically significant difference in NT or embryo length was detected (P = 0.271, 0.567). The difference in CRL could not be used to distinguish between sIUGR-type I and sIUGR-type II/III (P = 0.35). ROC analysis revealed that the difference in CRL predicted sIUGR with an area under the curve of 0.78; for comparison, the area under the curve for the prediction of TTTS was 0.51. The prediction of sIUGR using the CRL difference threshold of 7.38% had a sensitivity of 80.72% and a specificity of 67%, a positive predictive value (PPV) of 67%, and a negative predictive value (NPV) of 80.72%.

CONCLUSIONS

In MCDA twin pregnancies, the difference in the first-trimester CRL was valuable for predicting the occurrence of sIUGR but was not associated with TTTS. Embryo length and NT did not significantly differ among the groups.

TRIAL REGISTRATION

Not applicable.

Discordance in crown-rump length and nuchal translucency thickness in the prediction of adverse outcomes among monochorionic diamniotic twin pregnancies: A single-center retrospective cohort study from Vietnam

OBJECTIVE

To evaluate the usefulness of first-trimester crown-rump length (CRL) and nuchal translucency (NT) thickness discordance in predicting adverse outcomes in monochorionic diamniotic (MCDA) twin pregnancies.

METHODS

This retrospective cohort study enrolled MCDA twin pregnancies in which CRL and NT were measured at 11-13+6 weeks of pregnancy and collected for pregnancy outcomes between January 2022 and June 2023 at Tu Du Hospital in Vietnam. The intertwin discrepancy of CRL and NT was calculated as a percentage of the larger fetuses and smaller fetuses. Regression analysis was used to determine the significance of the association between the intertwin discordance in NT and CRL and the development of twin-to-twin transfusion syndrome (TTTS), fetal growth restriction (FGR), intrauterine fetal demise (IUFD), and those with normal outcomes. Receiver operating characteristic curves were constructed to evaluate the performance of inter-twin discrepancy in the prediction of FGR, TTTS, and IUFD.

RESULTS

A total of 294 MCDA twin pregnancies were studied. Among them, 149 cases (50.7%) had at least one adverse outcome. The complications included TTTS in 82 cases (55.0%), FGR in 89 cases (59.7%), one IUFD in 95 cases (63.8%), and two IUFDs in 19 cases (12.8%). CRL discordance greater than 10.0% and NT discordance greater than 20.0% were not related to TTTS and IUFD, only to FGR. A CRL discordance greater than 20.0% decreased the survival rate of fetuses. CRL discordance greater than 10.0% had specificity in diagnosing TTTS, IUFD, and FGR of more than 80%, whereas, NT discordance greater than 20.0% had specificity in detecting these complications of more than 50.0%. A predictive model including CRL and NT discordance showed a poor value with area under the curve of:0.69 (95% confidence interval 0.69-0.75).

CONCLUSION

In MCDA twin pregnancies, discordant CRL greater than 10.0% was related to FGR. Meanwhile, an intertwin discordance of NT thickness greater than 20.0% was not related to TTTS, FGR, and IUFD. However, adequate surveillance is still required.

ACR Appropriateness Criteria® Multiple Gestations: 2024 Update

The incidence of twin pregnancies has been rising, largely attributable to increasing use of artificial reproductive techniques. Ultrasound plays a critical role in establishing the chorionicity and amnionicity of multiple gestations, a key predictor of the expected risk and complications, along with guiding future clinical and imaging follow-up examinations and intervals. People carrying multiple gestations will typically undergo more ultrasound examinations (and occasionally fetal MRI) than those carrying singletons, at minimum including a first trimester dating scan, nuchal translucency scan at 11 to 14 weeks, an anatomy scan at 18 to 22 weeks, and other scans in the second and third trimesters for growth and surveillance. This document clarifies the most appropriate imaging guidelines for multiple gestations for seven clinical scenarios/variants, which range from initial imaging, follow-up imaging, growth and surveillance for uncomplicated multiple gestations, and those complicated by a known abnormality or discordance between fetuses. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

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.

The prognostic role of CRL discordance in first trimester ultrasound

OBJECTIVES

In the first trimester, intertwin crown-rump length (CRL) discordance has emerged as a notable factor linked to adverse perinatal health effects. It is frequently employed as a basis for counseling parents regarding potential adverse pregnancy outcomes. Despite its established association with adverse outcomes, the significance of CRL discordance in substantially predicting pregnancy problems and its efficacy in pregnancy screening remain subjects of ongoing discussion. The aim of this manuscript is to present current knowledge on CRL discordance.

METHODS

PubMed was searched for related articles with terms "Crown-Rump length", "Prenatal Screening", "Twin pregnancy", "Discordance".

RESULTS

Twenty-two studies were included in our study with six reporting data on monochorionic and 16 assessing the correlation between CRL discordance and adverse pregnancy outcomes. Fetal loss at the 20th and 24th week of the pregnancy, SGA neonates, pre-term delivery (32 weeks), perinatal death (24 weeks) are all reported adverse outcomes associated with CRL discordance. The reported cut-off for increased risk of adverse perinatal outcomes is a discordance of at least 10% or more.

CONCLUSIONS

Increased CRL (>10 %) discordance is linked to a higher risk of sFGR in both monochorionic and dichorionic pregnancies, fetal loss, and preterm delivery.

Clinical implications of crown-rump length discordance at 11 to 14 weeks in dichorionic twins

BACKGROUND

Crown-rump length discordance, defined as ≥10% discordance, has been investigated as an early sonographic marker of subsequent growth abnormalities and is associated with an increased risk of fetal loss in twin pregnancies. Previous studies have not investigated the prevalence of fetal aneuploidy or structural anomalies in twins with discordance or the independent association of crown-rump length discordance with adverse perinatal outcomes. Moreover, data are limited on cell-free DNA screening for aneuploidy in dichorionic twins with discordance.

OBJECTIVE

This study aimed to evaluate whether crown-rump length discordance in dichorionic twins between 11 and 14 weeks of gestation is associated with a higher risk of aneuploidy, structural anomalies, or adverse perinatal outcomes and to assess the performance of cell-free DNA screening in dichorionic twin pregnancies with crown-rump length discordance.

STUDY DESIGN

This was a secondary analysis of a multicenter retrospective cohort study that evaluated the performance of cell-free DNA screening for the common trisomies in twin pregnancies from December 2011 to February 2020. For this secondary analysis, we included live dichorionic pregnancies with crown-rump length measurements between 11 and 14 weeks of gestation. First, we compared twin pregnancies with discordant crown-rump lengths with twin pregnancies with concordant crown-rump lengths and analyzed the prevalence of aneuploidy and fetal structural anomalies in either twin. Second, we compared the prevalence of a composite adverse perinatal outcome, which included preterm birth at <34 weeks of gestation, hypertensive disorders of pregnancy, stillbirth or miscarriage, small-for-gestational-age birthweight, and birthweight discordance. Moreover, we assessed the performance of cell-free DNA screening in pregnancies with and without crown-rump length discordance. Outcomes were compared with multivariable regression to adjust for confounders.

RESULTS

Of 987 dichorionic twins, 142 (14%) had crown-rump length discordance. The prevalence of aneuploidy was higher in twins with crown-rump length discordance than in twins with concordance (9.9% vs 3.9%, respectively; adjusted relative risk, 2.7; 95% confidence interval, 1.4-4.9). Similarly, structural anomalies (adjusted relative risk, 2.5; 95% confidence interval, 1.4-4.4]) and composite adverse perinatal outcomes (adjusted relative risk, 1.2; 95% confidence interval, 1.04-1.3) were significantly higher in twins with discordance. A stratified analysis demonstrated that even without other ultrasound markers, there were increased risks of aneuploidy (adjusted relative risk, 3.5; 95% confidence interval, 1.5-8.4) and structural anomalies (adjusted relative risk, 2.7; 95% confidence interval, 1.5-4.8) in twins with CRL discordance. Cell-free DNA screening had high negative predictive values for trisomy 21, trisomy 18, and trisomy 13, regardless of crown-rump length discordance, with 1 false-negative for trisomy 21 in a twin pregnancy with discordance.

CONCLUSION

Crown-rump length discordance in dichorionic twins is associated with an increased risk of aneuploidy, structural anomalies, and adverse perinatal outcomes, even without other sonographic abnormalities. Cell-free DNA screening demonstrated high sensitivity and negative predictive values irrespective of crown-rump length discordance; however, 1 false-negative result illustrated that there is a role for diagnostic testing. These data may prove useful in identifying twin pregnancies that may benefit from increased screening and surveillance and are not ascertained by other early sonographic markers.

Intertwin nuchal translucency difference predicts the chance of co-twin death after fetal reduction in dichorionic triplet pregnancies: a retrospective analysis study

OBJECTIVES

To compare the clinical outcomes of different multifetal pregnancy reduction (MFPR) programs in dichorionic (DC) triplets, and explore the association between early ultrasound characteristics and co-twin death after potassium chloride (KCl) injection into one monochorionic (MC) twin.

METHODS

We retrospectively reviewed the data of DC triplets who underwent MFPR at our center during 2012-2021. Patients were grouped as follows: intracardiac KCl injection into one MC twin (group A), intracardiac KCl injection into both MC twins simultaneously (group B), and reduction of the singleton fetus (group C) and pregnancy outcomes were compared. Logistic regression was used to determine whether ultrasound measurements at 11-13+6 weeks predicted co-twin death and the receiver operator characteristic (ROC) analysis was conducted to assess the predictive performance.

RESULTS

Finally, we enrolled 184 patients. 153 cases were in group A, and 18, 13 cases were in group B and C respectively. Gestational age at the time of MFPR did not differ among the 3 groups (median: [Formula: see text] weeks). The survival rate was 89.6%, 88.9%, and 92.3% in group A, B, and C respectively, which was comparable among groups. Preterm birth was more common in group C (10/12, 83.3%). After KCl injection into one MC twin, co-twin death occurred in 86.3% cases (132/153) within 1 day; however, 3 patients had 2 live births each, with normal postnatal development. Intertwin nuchal translucency (NT) difference/discordance significantly predicted co-twin death within 1 day after MFPR, and the areas under the ROC curve were 0.694 and 0.689, respectively.

CONCLUSIONS

For MFPR in DC triplet pregnancies, reduction of the MC twins results in less preterm birth, and women with KCl injection into either one or both MC twins had similar outcomes. Large intertwin NT difference/discordance was associated with co-twin death within 1 day after KCl injection into one of the MC twins.

Chorionicity-associated variation in metabolic phenotype of cord blood in twin

BACKGROUND

Monochorionic (MC) twins present a higher incidence of unfavorable clinical perinatal outcomes than dichorionic (DC) twins, often in association with placental vascular anastomosis. In this study, we profiled the umbilical cord plasma metabolomes of uncomplicated MC and DC twin pregnancies and related these to several offspring outcomes, previously associated with birthweight.

METHODS

Umbilical vein blood samples were collected at birth from 25 pairs of uncomplicated MC twins and 24 pairs of uncomplicated DC twins. The samples were subjected to gas chromatography-mass spectrometry-based metabolomics. 152 metabolites were identified from the cord plasma samples of MC and DC twins. Partial least squares discriminant analysis and pathway analysis were performed to compare within DC/MC twin pairs and between DC and MC twins. A generalized estimating equation (GEE) model was utilized to explore the correlation between metabolic differences and birthweight discordance within and between twin pairs.

RESULTS

Our study revealed clear differences between the metabolite profiles of umbilical cord plasma of MC and DC twins. Metabolite profiles in MC within twin pairs and DC within twin pairs were characterized by the differences in 2 - hydroxyglutaramic acid levels and nicotinamide levels, respectively. The metabolic pathways of GSH, tryptophan, and fatty acid metabolism, were significantly downregulated in MC twins compared to DC twins. In addition, the concentration of caffeine and decamethyl-cyclopentasiloxane (D5) was positively correlated with birthweight in MC and DC twins.

CONCLUSION

This study demonstrated that the altered metabolites in umbilical plasma made contributions to the different chorionicities between uncomplicated MC twins and DC twins. The chorionicity of twins seems to affect the metabolic cross-talk between co-twin pairs and be related to birthweight discordance of twins.

Congenital heart defects in monochorionic twin pregnancy complicated by selective fetal growth restriction

OBJECTIVES

To evaluate the prevalence, subtypes and postnatal outcomes of congenital heart defects (CHD) in a cohort of monochorionic diamniotic (MCDA) twin pregnancies complicated by selective fetal growth restriction (sFGR), and to compare this population with a cohort of uncomplicated MCDA pregnancies evaluated during the same period.

METHODS

This was a retrospective analysis of all consecutive MCDA pregnancies referred between 2009 and 2018, including those complicated by sFGR (Group A) and those without complications (Group B). All neonates delivered in our center were screened for CHD before discharge. Discharge letters for all those delivered elsewhere were retrieved. Pregnancies with complications other than sFGR and those without perinatal follow-up were excluded. Pregnancies in Group A were divided into three types according to the Gratacós system of sFGR classification.

RESULTS

A total of 870 MCDA twin pregnancies were included: 296 in Group A and 574 in Group B. In Group A, the prevalence of CHD was 3.7% (22/592 twins), with no significant difference in CHD frequency between the three types of sFGR (Type I, 3.7%; Type II, 3.2%; Type III, 4.2%; P = 0.55). Of four Type-III sFGR pregnancies with CHD, one had pulmonary stenosis (PS) in the larger twin and isolated coarctation of the aorta in the smaller cotwin, and three had PS in the larger twin only. No Type-III sFGR pregnancies in which only the smaller twin was affected by CHD were observed. Of 11 CHD cases in the larger twin, 10 (91%) were right ventricular outflow tract abnormalities (RVOTA), and one (9%) was a ventricular septal defect. In the smaller twins, 11 cases of CHD were observed, covering a broad spectrum of cardiac abnormalities. In Group B, the CHD prevalence was 1.1% (13/1148 twins), which was similar to that in the general population, according to the EUROCAT registry for the same period and geographical area of the study (0.96%; P = 0.579). The CHD prevalence was significantly higher in Group A compared with Group B (3.7% vs 1.1%; P = 0.0002; odds ratio, 3.57 (95% CI, 1.78-7.22)). In all pregnancies with CHD in the study population, the anomaly was discordant.

CONCLUSIONS

In MCDA twin pregnancy, sFGR was associated with a three-fold higher prevalence of CHD. Women with such pregnancies should be referred to a tertiary care hospital for pre- and postnatal cardiac evaluation, treatment and long-term follow-up. In larger twins, the only major CHD observed was RVOTA, while a broad spectrum of CHD was noted in smaller twins. The higher risk of CHD in MCDA pregnancies appears to be due to the typical complications of the monochorionic pregnancy, rather than to the monochorionic nature of the pregnancy itself. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Intertwin growth discordance throughout gestation and hypertensive disorders of pregnancy

BACKGROUND

Previous studies have established the association between intertwin birthweight discordance and hypertensive disorders of pregnancy. However, longitudinal fetal size discordance concerning gestational hypertension or preeclampsia remains unclear.

OBJECTIVE

This study aimed to compare the patterns of estimated fetal weight discordance throughout gestation among normotensive women, women with gestational hypertension, and women with preeclampsia and to evaluate the association between crown-rump length discordance at 11 to 14 weeks of gestation and hypertensive disorders of pregnancy.

STUDY DESIGN

This was a retrospective cohort study of women with twin pregnancies who had antenatal care visits and delivered at a tertiary hospital between January 2013 and June 2021. The crown-rump length was measured at 11 to 14 weeks of gestation. Estimated fetal weight was calculated based on ultrasound examinations of fetal biometrics at 16 to 18, 20 to 24, 28 to 32, and ≥34 weeks of gestation, respectively. Crown-rump length and estimated fetal weight discordances were calculated: (larger crown-rump length - smaller crown-rump length)/larger crown-rump length × 100% and (larger estimated fetal weight - smaller estimated fetal weight)/larger estimated fetal weight × 100%, respectively. Multiple imputation was used to handle missing data, and all models accounted for the imputation. Multilevel model analysis was used to compare the differences in estimated fetal weight discordances throughout gestation among normotensive women, women with gestational hypertension, and women with preeclampsia. Generalized linear models were used to evaluate the association between crown-rump length discordance and hypertensive disorders of pregnancy, assuming a Poisson distribution. The possible nonlinear relationship between continuous crown-rump length discordance and hypertensive disorders of pregnancy was examined by generalized additive models. All analyses were stratified by chorionicity.

RESULTS

Of the 3280 women with twin pregnancies who met the inclusion criteria, 187 (5.7%) developed gestational hypertension, and 436 (13.3%) developed preeclampsia, including 125 (3.8%) early-onset preeclampsia and 311 (9.5%) late-onset preeclampsia. In women with dichorionic twin pregnancies, compared with normotensive women, a substantial progression of estimated fetal weight discordance throughout pregnancy was identified in women who developed preeclampsia, and a large progression of estimated fetal weight discordance in late pregnancy was identified in women who developed gestational hypertension. In women with monochorionic twin pregnancies, estimated fetal weight discordances were more progressive from 20 to 24 weeks of gestation onward in women who developed preeclampsia than in normotensive women. Crown-rump length discordance at 11 to 14 weeks of gestation was associated with an increased risk of preeclampsia (relative risk, 1.03; 95% confidence interval, 1.00-1.05), particularly early-onset preeclampsia (relative risk, 1.09; 95% confidence interval, 1.04-1.13). A crown-rump length discordance of ≥10% had 1.2 times the increased risk of developing early-onset preeclampsia (relative risk, 2.27; 95% confidence interval, 1.28-4.03). This association was identified in dichorionic twins, but not in monochorionic twins.

CONCLUSION

Our study demonstrated distinct growth discordant patterns among normotensive women, women with gestational hypertension, and women with preeclampsia in twin pregnancies. Intertwin crown-rump length discordance at 11 to 14 weeks of gestation was associated with an increased risk of preeclampsia, especially early-onset preeclampsia in dichorionic twin pregnancies, with a dose-response pattern.

The Association between Intertwin Difference in First Trimester Crown-Rump Length, Nuchal Translucency, and Birth Weight Discordance in Twin Pregnancies: A Retrospective Cohort Study

Background. Discordant birth weight in twins is linked to poor outcomes and predicting this discrepancy may lead to enhanced screening and surveillance. Our purpose was to quantify the relationship between intertwin nuchal translucency (NT) and crown-rump length (CRL) discordance with birth weight discrepancies ≥ 20%. Methods. We conducted a retrospective cohort study of 887 live twin births delivering at a Canadian tertiary care center over a 7-year period who opted for integrated prenatal screening. Categorical data are presented as numbers and percentages, and continuous data are expressed as means and standard deviations. Chi-square tests, Fisher’s Exact tests, or $T$ -test were performed as appropriate. We then used published data and receiver operating curves to determine the optimal thresholds for predicting birth weight discordance based on first trimester intertwin NT differences. These values were used in multivariate logistic regression models accounting for known confounders. Results. Roughly 16% of twin pairs exhibited ≥ 20% difference in birth weight. Twin pairs with a CRL discordance greater than 10% have nearly a 4 times greater likelihood of having a birth weight discordance greater than 20% (OR 3.71, CI 2.24-6.14) while controlling for chorionicity, maternal age, gestational age at delivery, maternal body mass index (BMI), and parity. In these models, intertwin NT discordance ≥ 20% (OR 1.16, CI 0.77-1.77) and NT discordance ≥ 14% (OR 1.08, CI 0.73-1.60) were not statistically significant predictors of twin birth weight differences. However, when evaluating the effect of the larger intertwin NT value corresponding to the 95th percentile, an NT difference ≥ 0.9 mm was predictive of birth weight discordance ≥ 20% (OR 2.53, CI 1.21-5.29). Conclusion. Although intertwin CRL and NT discordance measured via ultrasound between 11-14 weeks gestation are related to birth weight discordance, there is uncertainty as to whether twin birth weight differences are related to adverse pregnancy outcomes in this population.

Guideline No. 428: Management of Dichorionic Twin Pregnancies

OBJECTIVE

To review evidence-based recommendations for the management of dichorionic twin pregnancies.

TARGET POPULATION

Pregnant women with a dichorionic twin pregnancy.

BENEFITS, HARMS, AND COSTS

Implementation of the recommendations in this guideline may improve the management of twin pregnancies and reduce neonatal and maternal morbidity and mortality.

EVIDENCE

Published literature was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary (e.g., twin, preterm birth). Results were restricted to systematic reviews, randomized controlled trials, 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 weak recommendations).

INTENDED AUDIENCE

Obstetricians, family physicians, nurses, midwives, maternal-fetal medicine specialists, radiologists, and other health care providers who care for women with twin pregnancies.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Amyoplasia in monochorionic monozygotic pregnancy following interstitial laser

Amyoplasia is a specific form of arthrogryposis, without any genetic cause. Six to ten percent of amyoplasia cases are one of the monozygotic twins, with the other twin being normal. Failure of maturation of anterior horn cells (AHCs) due to ischemic injury has been postulated as the primary pathological change, leading to arrest in the development of muscle fibers supplied by the affected AHCs with the typical limb positioning seen in amyoplasia. Twin-to-twin transfusion syndrome (TTTS) is an important risk factor for ischemic injury in monozygotic twin pregnancies. We present a case of monochorionic diamniotic twin pregnancy with features of TTTS at 12 weeks who underwent interstitial laser followed by the development of lower limb akinesia in the surviving fetus. Possible causes of amyoplasia are discussed.

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.

Special Considerations Regarding Antenatal Care and Pregnancy Complications in Dichorionic Twin Pregnancies

Twin pregnancies account for about 3.3% of all deliveries in the United States with the majority of them being dichorionic diamniotic (DCDA). Maternal physiological adaption in twin pregnancies is exaggerated and the rate of almost every maternal and fetal complication is higher when compared to singleton pregnancies. Therefore, twin pregnancies necessitate closer antenatal surveillance by care providers who are familiar with the specific challenges unique to these pregnancies, and there is evidence that following women with twins in a specialized twin clinic can result in improved obstetrical outcomes. The importance of the first antenatal visit in twin pregnancies cannot be over emphasized and should preferably take place early in gestation as it is the optimal period to correctly identify the number of fetuses and the type of placentation (chorionicity and amnionicity). This will allow the patients, families, and caregivers to make the appropriate modifications and to tailor an optimal antenatal follow-up plan. This plan should focus on general recommendations such as weight gain and level of activity, education regarding complications specific to twin pregnancies along with the relevant symptoms and indications to seek care, as well as on close maternal and fetal monitoring. In this review, we summarize available evidence and current guidelines regarding antenatal care in DCDA twin pregnancies.

Crown-rump length measurement error: impact on assessment of growth

OBJECTIVE

To examine the impact of first-trimester crown-rump length (CRL) measurement error on the interpretation of estimated fetal weight (EFW) and classification of fetuses as small-, large- or appropriate-for-gestational age on subsequent growth scans.

METHODS

We examined the effects of errors of ± 2, ± 3 and ± 4 mm in the measurement of fetal CRL on percentiles of EFW at 20, 32 and 36 weeks' gestation and classification as small-, large- or appropriate-for-gestational age. Published data on CRL measurement error were used to determine variation present in practice.

RESULTS

A measurement error of -2 mm in first-trimester CRL shifts an EFW on the 10^th percentile at the 20-week scan to around the 20^th percentile, and the effect of a CRL measurement error of + 2 mm would shift an EFW on the 10^th percentile to around the 5^th percentile. At 32 weeks, a first-trimester CRL measurement error would shift an EFW on the 10^th percentile to the 7^th (+ 2 mm) or 14^th (-2 mm) percentile; at 36 weeks, the EFW would shift from the 10^th percentile to the 8^th (+ 2 mm) or 12^th (-2 mm) percentile. Published data suggest that measurement errors of 2 mm or more are common in practice.

CONCLUSION

Because of the widespread and potentially severe consequences of CRL measurement errors as small as 2 mm on clinical assessment, patient management and research results, there is a need to increase awareness of the impact of CRL measurement error and to reduce measurement error variation through standardization and quality control. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Clinical Practice Guidelines for Prenatal Aneuploidy Screening and Diagnostic Testing from Korean Society of Maternal-Fetal Medicine: (2) Invasive Diagnostic Testing for Fetal Chromosomal Abnormalities

The Korean Society of Maternal Fetal Medicine proposed the first Korean guideline on prenatal aneuploidy screening and diagnostic testing, in April 2019. The clinical practice guideline (CPG) was developed for Korean women using an adaptation process based on good-quality practice guidelines, previously developed in other countries, on prenatal screening and invasive diagnostic testing for fetal chromosome abnormalities. We reviewed current guidelines and developed a Korean CPG on invasive diagnostic testing for fetal chromosome abnormalities according to the adaptation process. Recommendations for selected 11 key questions are: 1) Considering the increased risk of fetal loss in invasive prenatal diagnostic testing for fetal genetic disorders, it is not recommended for all pregnant women aged over 35 years. 2) Because early amniocentesis performed before 14 weeks of pregnancy increases the risk of fetal loss and malformation, chorionic villus sampling (CVS) is recommended for pregnant women who will undergo invasive prenatal diagnostic testing for fetal genetic disorders in the first trimester of pregnancy. However, CVS before 9 weeks of pregnancy also increases the risk of fetal loss and deformity. Thus, CVS is recommended after 9 weeks of pregnancy. 3) Amniocentesis is recommended to distinguish true fetal mosaicism from confined placental mosaicism. 4) Anti-immunoglobulin should be administered within 72 hours after the invasive diagnostic testing. 5) Since there is a high risk of vertical transmission, an invasive prenatal diagnostic testing is recommended according to the clinician's discretion with consideration of the condition of the pregnant woman. 6) The use of antibiotics is not recommended before or after an invasive diagnostic testing. 7) The chromosomal microarray test as an alternative to the conventional cytogenetic test is not recommended for all pregnant women who will undergo an invasive diagnostic testing. 8) Amniocentesis before 14 weeks of gestation is not recommended because it increases the risk of fetal loss and malformation. 9) CVS before 9 weeks of gestation is not recommended because it increases the risk of fetal loss and malformation. 10) Although the risk of fetal loss associated with invasive prenatal diagnostic testing (amniocentesis and CVS) may vary based on the proficiency of the operator, the risk of fetal loss due to invasive prenatal diagnostic testing is higher in twin pregnancies than in singleton pregnancies. 11) When a monochorionic twin is identified in early pregnancy and the growth and structure of both fetuses are consistent, an invasive prenatal diagnostic testing can be performed on one fetus alone. However, an invasive prenatal diagnostic testing is recommended for each fetus in cases of pregnancy conceived via in vitro fertilization, or in cases in which the growth of both fetuses differs, or in those in which at least one fetus has a structural abnormality. The guidelines were established and approved by the Korean Academy of Medical Sciences. This guideline is revised and presented every 5 years.

A case of heteropaternal superfecundation identified by microhap sequencing of maternal plasma cell-free DNA: A case of HS identified by microhap sequencing

Heteropaternal superfecundation (HS) refers to the fertilization of two or more oocytes by spermatozoa from different male partners during the polyovulatory period. The present study reported a newly discovered case of HS in the 10th week of gestation, in a case of disputed paternity involving a pair of female twins and two alleged fathers (AF₁ and AF₂), based on a custom-designed microhap sequencing assay and R package relMix for data interpretation. The results suggested that the twins had different biological fathers, e.g., HS, and indicated the paternity of AF₁ in relation to one of the twins while excluding AF₂ with regard to both twins. Standard short tandem repeat (STR) analysis was employed to confirm the paternity of the heteropaternal twins. The reported case indicates that HS may occur in paternity cases with dizygotic twins, and microhap, as a novel type of highly polymorphic marker proved to be suitable for mixture deconvolution, should be able to resolve this question effectively and noninvasively at the early stage of pregnancy.

Predictive value of prenatal ultrasound parameters for dichorionic growth discordant twins

BACKGROUND

Twin growth discordance was demonstrated to be a risk factor for adverse perinatal outcomes, and prenatal ultrasonographic methods were utilized to predict twin growth discordance to improve outcomes. The results currently reported are not consistent due to the poor unified parameters and gestational durations.

METHODS

A total of 71 dichorionic twins with growth discordance and 346 dichorionic twins with normal growth were respectively included in the retrospective cohort study. The weight discordance of more than 25% was defined as a "growth discordant twin". The clinical baseline information, maternal outcomes, twin birth weights and fetal growth parameters (which were measured by ultrasound) were compared between the two groups from early gestation to late gestation. Multiple logistic regression and receiver operating characteristic curves were adopted to evaluate the predictive value of the growth parameters.

RESULTS

Compared with normal dichorionic twins, the clinical baseline conditions were similar in the twins those finally developed growth discordance. The fetal growth parameters and the deepest volume pocket of amniotic fluid in early and mid-pregnancy showed no obvious predictive values. The fetal growth parameters in late pregnancy showed predictive values, especially the discordance of estimated fetal weight (EFW) in the early third-trimester (P < 0.001, area under the curve, 0.822; the cut-off value, 20%; sensitivity, 66.67%; specificity, 91.30%; positive predictive value, 88.46%).

CONCLUSION

Two assessment approaches were suggested and adopted to predict twin growth discordance in the current study. Twin growth should be assessed longitudinally and dynamically. Normal twins may show growth imbalance in the early stage. The discordance of EFW in late pregnancy may be a useful indicator for a growth discordance of more than 25%, which is required further confirmation.

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.

Diagnosis of fetal defects in twin pregnancies at routine 11-13-week ultrasound examination

OBJECTIVES

To examine the performance of the routine 11-13-week scan in detecting fetal defects in twin pregnancies and to examine if, in pregnancies with a fetal defect, compared to those with normal fetuses, there is increased incidence of nuchal translucency thickness (NT) ≥ 95^th and ≥ 99^th percentiles or intertwin discordance in crown-rump length (CRL) ≥ 10% and ≥ 15%.

METHODS

This was a retrospective analysis of prospectively collected data in twin pregnancies undergoing routine ultrasound examination for fetal anatomy, according to standardized protocols, at 11-13 weeks' gestation between 2002 and 2019. Pregnancies with known chromosomal abnormality were excluded. The final diagnosis of fetal defect was based on the results of postnatal examination in cases of live birth and on the findings of the last ultrasound examination in cases of pregnancy termination, miscarriage or stillbirth. The performance of the 11-13-week scan in the detection of fetal defects was determined.

RESULTS

The study population of 6366 twin pregnancies with two live fetuses at 11-13 weeks' gestation included 4979 (78.2%) dichorionic (DC) and 1387 (21.8%) monochorionic (MC) twin pregnancies. The main findings were: first, the overall incidence of fetal defects was higher in MC than in DC twins (2.8% vs 1.3%); second, the proportion of defects diagnosed in the first trimester was higher in MC than in DC twins (52.6% vs 27.1%); third, the pattern of defects in relation to detectability at the 11-13-week scan (always detectable, sometimes detectable and never detectable) was similar to that reported previously in singleton pregnancies; fourth, always-detectable defects included acrania, alobar holoprosencephaly, encephalocele, pentalogy of Cantrell, exomphalos, body-stalk anomaly, twin reversed arterial perfusion sequence and conjoined twins; fifth, the incidence of fetal NT ≥ 95^th percentile was higher in those with than in those without a defect (16.5% vs 4.5% in DC twins and 19.2% vs 5.9% in MC twins) and this was also true for NT ≥ 99^th percentile (8.3% vs 1.0% in DC twins and 15.4% vs 2.0% in MC twins); and sixth, the incidence of CRL discordance ≥ 10% was higher in those with than in those without a defect (20.2% vs 7.9% in DC twins and 33.8% vs 9.3% in MC twins) and this was also true for CRL discordance ≥ 15% (10.1% vs 1.9% in DC twins and 28.2% vs 2.8% in MC twins).

CONCLUSIONS

First, fetal defects are more common in MC than in DC twin pregnancies. Second, first-trimester detection of fetal defects in DC twin pregnancies is similar to that in singleton pregnancies. Third, first-trimester detectability of defects in MC twins is higher than in DC twins. Fourth, in twin pregnancies with a fetal defect, there is higher intertwin discordance in CRL and incidence of increased NT, but the predictive performance of screening by these markers is poor. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

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.