Prediction of outcome in twin pregnancy with first and early second trimester ultrasound

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.

Investigation of the Association of Abdominal Circumference Discord-ance and Estimated Fetal Weight Discordance in Twins with Birth Weight Discordance

Background

Twin pregnancy is associated with a high risk of mortality and morbidity. It is necessary to estimate the weight difference of the fetuses with a reliable method to prevent possible complications. This study was conducted to compare the association between the Estimated fetal weight (EFW) discord-ance and the Abdominal Circumference (AC) discordance with birth weight in twins.

Methods

This was a descriptive-analytical and retrospective study. The statistical population was all twin pregnant mothers referred to Imam Khomeini Hospital in Ahvaz from 2017 to 2019. The sample size was determined with a census (540 people). Based on AC , the size of head circumference (HC), femur length (FL), and the Biparietal Diameter (BPD), EFW was calculated. Then the EFW Dis-cordance and AC Discordance were calculated and compared with the birth weight. Data were analyzed using SPSS18. Unpaired, Two-Tailed T-test and Pearson correlation test were used.

Results

The results showed that the mean discordance of fetal weight in twin pregnancies in the EFW method was 9.25%, in the AC method was 9.89% and finally, at birth, was 10.72%. The correla-tion of the weight difference between the two embryos in the AC method with the time of birth (r = 0.922 and P < 0.001) was higher than in the EFW method with the time of birth (r = 0.69 and P < 0.001) and finally, it was found that in detecting the discordance more than 20% and 25%, AC diagnostic power was good, but EFW was moderate.

Conclusion

Therefore, to evaluate the weight and weight difference in twin embryos, the AC method has the appropriate accuracy and compatibility. Another major prospective study to evaluate the diagnostic performance of AC and EFW mismatch based on gestational age at scan, incision point, and maternal and placental characteristics to determine true ultrasound diagnostic accuracy in predict-ing growth mismatch in twin pregnancy and optimal post-case management option is needed.

Concordance of the risk of neonatal respiratory morbidity assessed by quantitative ultrasound lung texture analysis in fetuses of twin pregnancies

To evaluate the concordance of the risk of neonatal respiratory morbidity (NRM) assessed by quantitative ultrasound lung texture analysis (QuantusFLM) between twin fetuses of the same pregnancy. Prospective study conducted in twin pregnancies. Fetal ultrasound lung images were obtained at 26.0–38.6 weeks of gestation. Categorical (high or low) and continuous results of the risk of NRM were compared between twins. Fetal ultrasound lung images from 131 pairs (262 images) of twins were included. The images were classified into three gestational age ranges: Group 1 (26.0–29.6 weeks, 78 images, 39 pairs [29.8%]); Group 2 (30.0–33.6 weeks, 98 images, 49 pairs [37.4%]) and Group 3 (34.0–38.6 weeks, 86 images, 43 pairs [32.8%]). Concordance was good in Groups 1 and 3 and moderate in Group 2. In Groups 2 and 3 at least one fetus presented high-risk results in 26.5% and 11.6% of twin pairs, respectively. Only gestational age < 32 weeks, gestational diabetes mellitus, and spontaneous conception were associated with a high risk of NRM in Group 2. There was good concordance of the risk of NRM between twins < 30.0 weeks and > 34.0 weeks. From 30.0 to 33.6 weeks 26.5% of the twin pairs had discordant results, with moderate concordance of the risk of NRM.

The accuracy of prenatal diagnosis of selective fetal growth restriction with second trimester Doppler ultrasound in monochorionic diamniotic twin pregnancies

BACKGROUND

Selective fetal restriction growth (sFGR) is one of the common diseases of monochorionic diamniotic (MCDA) twin pregnancies, resulting in many adverse outcomes. At present, second trimester ultrasonography is widely used in the prenatal diagnosis of sFGR, but the diagnostic effectiveness is still uncertain. The aim of this study is to assess the diagnostic accuracy of second trimester Doppler ultrasound measurements for sFGR.

METHODS

A retrospective study included 280 pregnant women (118 with and 162 without sFGR) with MCDA pregnancies was conducted in the fetal medicine center from Leiden University Medical Center from January 2008 to December 2013. The women participating had already undergone an ultrasound examination in the second trimester. The postnatal criteria of sFGR was a single birth weight (BW) < 3 rd percentile in a twin, or birth weight discordance (BWD)≥25% between two twins, while the BW of the smaller twin < 10th percentile. Early prenatal diagnosis of sFGR was defined as a single EFW < 3 rd percentile in a twin, or at least 2 of the following 4 parameters must be met (fetal weight of one fetus < 10th percentile, AC of one fetus <10th percentile, EFW discordance≥25%, UA pulsatility index (PI) of the smaller fetus > 95th percentile). According to the diagnosis of sFGR after birth, we evaluate diagnostic effectiveness of Doppler ultrasound in the second trimester for sFGR.

RESULTS

Of these 280 participants, the mean age was 32.06 ± 4.76 years. About 43.9% of pregnant women were primiparas. The ability of second trimester Doppler ultrasound to accurately diagnosed sFGR is 75.4%, missed diagnosis rate and the misdiagnosis rate were 24.6% and 10.5% respectively. The ROC curve indicated that the combination of AC discordance, EFW discordance, and small fetal UA blood flow was the best diagnostic indicator of sFGR in MCDA pregnancy with the AUC was 0.882 (95%CI, 0.839-0.926).

CONCLUSIONS

Second trimester Doppler and ultrasound measurements is an effective method for early prenatal diagnosis of sFGR. The combined indicator of AC discordance, EFW discordance, and the small fetal UA blood flow reaches highest diagnostic value.

Second-trimester abdominal circumference discordance and adverse perinatal outcomes in monochorionic twins

OBJECTIVE

The perinatal outcomes in second-trimester abdominal circumference (AC) discordant twins are yet to be established. The aim of this study was to ascertain perinatal risks associated with second-trimester AC discordance in monochorionic (MC) twins.

METHOD

We conducted a retrospective study of all MC twin pregnancies over a 7-year period. Intertwin AC discordance at 14-26 gestational weeks was analyzed in relation to Doppler abnormalities, obstetric complications, and perinatal adverse outcomes.

RESULTS

A total of 246 MC twin pregnancies were included in the analysis. The smaller twins of second-trimester AC discordant pairs were at increased prevalence of abnormal umbilical artery flow (50% versus 24%, p < .001) and low positive A wave of ductus venous flow (24% versus 9%, p = .002). The second-trimester AC discordant twins were at increased risk of oligohydramnios in smaller twin (OR = 2.44, 95% CI = 1.37-4.32, p < .01), cardiomegaly in larger twin (OR = 2.95, 95% CI = 1.01-8.60, p < .05), birth weight of either twin below the 10th percentile for gestational age (OR = 5.56, 95% CI = 2.67-11.59, p < .001), birth weight discordance > 25% (OR = 9.41, 95% CI = 4.46-19.87, p < .001), IUFD (OR = 3.26, 95% CI = 1.76-6.05, p < .001), and severe neonatal morbidity (OR = 1.83, 95% CI = 1.03-3.26, p < .05). The intact survival rate in discordant and concordant twin pairs was 70% and 89%, respectively (p < .001).

CONCLUSIONS

Early and increase fetal surveillance of the second-trimester AC discordant twins should be utilized to establish perinatal risks, thus allowing prenatal care to improve.

Ultrasound for diagnosis of birth weight discordance in twin pregnancies

BACKGROUND

There is a need to standardize monitoring in obstetric research of twin pregnancies. Identification of birth weight discordance (BWD), defined as a difference in the birth weights of twins, is a well-documented phenomenon in twin pregnancies. Ultrasound for the diagnosis of BWD informs complex decision making including whether to intervene medically (via laser photo coagulation) or deliver the twins to avoid fetal morbidities or even death. The question is, how accurate is this measurement?

OBJECTIVES

To determine the diagnostic accuracy (sensitivity and specificity) of ultrasound estimated fetal weight discordance (EFWD) of 20% and 25% using different estimated biometric ultrasound measurements compared with the actual BWD as the reference standard in twin pregnancies.

SEARCH METHODS

The search for this review was performed on 15 March 2019. We searched CENTRAL, MEDLINE (Ovid), Embase (Ovid), seven other databases, conference proceedings, reference lists and contacted experts. There were no language or date restrictions applied to the electronic searches, and no methodological filters to maximize sensitivity.

SELECTION CRITERIA

We selected cohort-type studies with delayed verification that evaluated the accuracy of biometric measurements at ultrasound scanning of twin pregnancies that had been proposed for the diagnosis of estimated BWD, compared to BWD measurements after birth as a reference standard. In addition, we only selected studies that considered twin pregnancies and applied a reference standard for EFWD for the target condition of BWD.

DATA COLLECTION AND ANALYSIS

We screened all titles generated by electronic database searches. Two review authors independently assessed the abstracts of all potentially relevant studies. We assessed the identified full papers for eligibility, and extracted data to create 2 × 2 tables. Two review authors independently performed quality assessment using the QUADAS-2 tool. We excluded studies that did not report data in sufficient detail to construct 2 × 2 tables, and where this information was not available from the primary investigators. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 39 eligible studies with a median study sample size of 140. In terms of risk of bias, there were many unclear statements regarding patient selection, index test and use of proper reference standard. Twenty-one studies (53%) were of methodological concern due to flow and timing. In terms of applicability, most studies were of low concern. Ultrasound for diagnosis of BWD in twin pregnancies at 20% cut-off Twenty-two studies provided data for a BWD of 20% and the summary estimate of sensitivity was 0.51 (95% CI 0.42 to 0.60), and the summary estimate of specificity was 0.91 (95% CI 0.89 to 0.93) (8005 twin pregnancies; very low-certainty evidence). Ultrasound for diagnosis of BWD in twin pregnancies at 25% cut-off Eighteen studies provided data using a BWD discordance of 25%. The summary estimate of sensitivity was 0.46 (95% CI 0.26 to 0.66), and the summary estimate of specificity was 0.93 (95% CI 0.89 to 0.96) (6471 twin pregnancies; very low-certainty evidence). Subgroup analyses were possible for both BWD of 20% and 25%. The diagnostic accuracy did not differ substantially between estimation by abdominal circumference and femur length but femur length had a trend towards higher sensitivity and specificity. Subgroup analyses were not possible by sex of twins, chorionicity or gestational age due to insufficient data.

AUTHORS' CONCLUSIONS

Very low-certainty evidence suggests that EFWD identified by ultrasound has low sensitivity but good specificity in detecting BWD in twin pregnancies. There is uncertain diagnostic value of EFWD; this review suggests there is insufficient evidence to support this index as the sole measure for clinical decision making to evaluate the prognosis of twins with growth discordance. The diagnostic accuracy of other measures including amniotic fluid index and umbilical artery Doppler resistive indices in combination with ultrasound for clinical intervention requires evaluation. Future well-designed studies could also evaluate the impact of chorionicity, sex and gestational age in the diagnostic accuracy of ultrasound for EFWD.

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.

ACR Appropriateness Criteria® Multiple Gestations

Women with twin or higher-order pregnancies will typically have more ultrasound examinations than women with a singleton pregnancy. Most women will have at minimum a first trimester scan, a nuchal translucency evaluation scan, fetal anatomy scan at 18 to 22 weeks, and one or more scans in the third trimester to evaluate growth. Multiple gestations are at higher risk for preterm delivery, congenital anomalies, fetal growth restriction, placenta previa, vasa previa, and velamentous cord insertion. Chorionicity and amnionicity should be determined as early as possible when a twin pregnancy is identified to permit triage of the monochorionic group into a closer surveillance model. Screening for congenital heart disease is warranted in monochorionic twins because they have an increased rate of congenital cardiac anomalies. In addition, monochorionic twins have a higher risk of developing cardiac abnormalities in later gestation related to right ventricular outflow obstruction, in particular the subgroups with twin-twin transfusion syndrome or selective intrauterine growth restriction. Monochorionic twins have unique complications including twin-to-twin transfusion syndrome, twin embolization syndrome, and acardius, or twin-reversed arterial perfusion sequence. 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 include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Diagnostic accuracy of ultrasound in predicting birth-weight discordance in twin pregnancy: systematic review and meta-analysis

OBJECTIVE

To investigate the diagnostic performance of ultrasound in predicting birth-weight (BW) discordance in twin pregnancy.

METHODS

Electronic databases PubMed, EMBASE and CINAHL were searched using combinations of MeSH terms 'birth weight', 'discordance', 'twins' and 'ultrasound'. Summary estimates of sensitivity, specificity, positive and negative likelihood ratios and diagnostic odds ratios for the predictive accuracy of sonographically estimated fetal-weight (EFW) discordance and abdominal-circumference (AC) discordance in predicting BW discordance were computed using hierarchical summary receiver-operating characteristics curves.

RESULTS

Twenty studies (including 5826 twin pregnancies) were included. EFW discordance ≥ 20% had a sensitivity of 65.4% and specificity of 90.8% in predicting BW discordance ≥ 20%. The predictive performance of ultrasound performed within 1 month, 2 weeks and 3 days before birth was 61.4%, 72.3% and 78.9%, respectively. EFW discordance ≥ 25% had a sensitivity of 57.7% and specificity of 95.2% in predicting BW discordance ≥ 25%. The sensitivity of EFW discordance ≥ 25% detected within 1 month, 2 weeks and 3 days before birth was 60.0%, 75.0% and 60.3%, respectively, while the corresponding values for specificity were 97.7%, 96.2% and 87.3%, respectively. In view of the different cut-offs reported among studies, it was not possible to perform comprehensive data synthesis for each AC discordance cut-off. The optimal diagnostic performance of AC discordance was for prediction of BW discordance ≥ 25%, with a sensitivity of 70.8% and specificity of 86.4%.

CONCLUSION

Ultrasound EFW discordance has an overall moderate accuracy in predicting BW discordance in twin pregnancy. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Prenatal prediction of significant intertwin birthweight discordance using standard second and third trimester sonographic parameters

INTRODUCTION

Our study aim was to evaluate standard ultrasound-derived fetal biometric parameters in the prediction of clinically significant intertwin birthweight discordance defined as ≥18%.

MATERIAL AND METHODS

This was a secondary analysis of a prospective cohort study of 1028 unselected twin pairs recruited over a two-year period. Dichorionic twins underwent two-weekly ultrasonographic surveillance from 24 weeks' gestation, with surveillance of monochorionic twins two-weekly from 16 weeks. Ultrasonographic biometric data from 24 to 36 weeks were evaluated for the prediction of an intertwin birthweight discordance threshold ≥18%. Umbilical artery Doppler waveform data was also analyzed to evaluate whether it was predictive of birthweight discordance.

RESULTS

Of the 956 twin pairs analyzed for discordance, 208 pairs were found to have a clinically significant birthweight discordance ≥18%. All biometric parameters were predictive of significant inter-twin birthweight discordance at low cut-offs, with low discriminatory powers when ROC curves were analyzed. Discordance in estimated fetal weight was predictive of a significant birthweight discordance at all gestational categories with cut-offs between 8 and 11%. A low-discriminatory power and poor sensitivity and specificity were also observed. An abnormal umbilical artery Doppler was predictive of birthweight discordance ≥18% between 28 and 32 weeks' gestation, although with poor sensitivity and specificity.

CONCLUSIONS

Calculation of estimated fetal weight and birthweight discordance between twins allows minimal margin for error. These margins make it difficult to accurately predict those who are at or above the discordance threshold of 18%. These findings highlight that small intertwin discrepancies in weight and biometry should not be overlooked and merit further investigation.

Prediction of birth weight discordance from fetal weight estimations at 21-24 weeks' scans in monochorionic and dichorionic twins

OBJECTIVE

To evaluate if inter-twin estimated fetal weight (EFW) differences at 21-24 weeks' scans predict birth weight discordance in monochorionic and dichorionic twins born at three gestational age periods.

METHODS

We counted the number of pairs with discordant EFWs (EFWs greater than the mean + 1SD; i.e. a difference above 12% in dichorionic and 21% in monochorionic twins) derived during a 21-24 weeks' scan as compared to actual discordant birth weight (>25%) in monochorionic and dichorionic pairs born at ≤32, 33-36 and >36 weeks.

RESULTS

We studied 416 dichorionic and 244 monochorionic twins. The frequency of EFWs discordance at 21-24 weeks was the same for dichorionic and monochorionic twins but the total number of birth weight discordant pairs was significantly smaller among dichorionic twins (OR 0.2, 95% CI 0.1, 0.6). Generally, the positive predictive values for birth weight discordance by using the EFWs difference were quite poor, but always better in monochorionic than in dichorionic twins. Whereas the negative predictive value and hence the sensitivity for monochorionic twins was 100% irrespective of gestational age at birth, it was much lower in the dichorionic pairs.

CONCLUSION

Concordant EFWs at 21-24 weeks exclude discordant birth weight in monochorionic twins whereas discordant EFWs are poor predictors of birth weight discordance especially in dichorionic twins irrespective when the twins were born.

Multiple gestations and preterm birth

Preterm birth is a major concern in modern obstetrics, and an important source of morbidity and mortality in newborns. Among twin pregnancies, especially, preterm birth is highly prevalent, and it accounts for almost 50% of the complications observed in this obstetrical population. In this article, we review the existing literature regarding the prediction and prevention of preterm birth in both symptomatic and asymptomatic twin pregnancies. In asymptomatic twin pregnancies, the best two predictive tests were cervical length (CL) measurement and cervicovaginal fetal fibronectin (fFN) testing. A single measurement of transvaginal CL at 20-24 weeks of gestation <20 mm or <25 mm is a good predictor of spontaneous preterm birth at <28, <32, and <34 weeks of gestation. A CL beyond 25 mm is associated with a 2% risk for birth before 28 weeks and with a 65% chance for a term pregnancy. Cervicovaginal fFN may be slightly less accurate than CL; however, it has a high negative predictive value in women presenting with threatened preterm labor, as <2% of these women will deliver within one week if the fFN is negative. In symptomatic twin pregnancies, no tests have proven accurate in predicting the risk of preterm birth. For the prevention of preterm birth in asymptomatic twins, regardless of CL, no treatment including bed rest, limitation of home activities, prophylactic tocolysis, progesterone, or cerclage has been shown to reduce the rate of preterm birth. Cervical pessaries might be of interest in cases where there is a short cervix (<25 mm and <38 mm, respectively) but these results need to confirmed in future trials.

Prediction of preterm birth in twin gestations using biophysical and biochemical tests

The objective of this study was to determine the performance of biophysical and biochemical tests for the prediction of preterm birth in both asymptomatic and symptomatic women with twin gestations. We identified a total of 19 tests proposed to predict preterm birth, mainly in asymptomatic women. In these women, a single measurement of cervical length with transvaginal ultrasound before 25 weeks of gestation appears to be a good test to predict preterm birth. Its clinical potential is enhanced by the evidence that vaginal progesterone administration in asymptomatic women with twin gestations and a short cervix reduces neonatal morbidity and mortality associated with spontaneous preterm delivery. Other tests proposed for the early identification of asymptomatic women at increased risk of preterm birth showed minimal to moderate predictive accuracy. None of the tests evaluated in this review meet the criteria to be considered clinically useful to predict preterm birth among patients with an episode of preterm labor. However, a negative cervicovaginal fetal fibronectin test could be useful in identifying women who are not at risk for delivering within the next week, which could avoid unnecessary hospitalization and treatment. This review underscores the need to develop accurate tests for predicting preterm birth in twin gestations. Moreover, the use of interventions in these patients based on test results should be associated with the improvement of perinatal outcomes.

Does early second-trimester sonography predict adverse perinatal outcomes in monochorionic diamniotic twin pregnancies?

OBJECTIVES

To determine whether intertwin discordant abdominal circumference, femur length, head circumference, and estimated fetal weight sonographic measurements in early second-trimester monochorionic diamniotic twins predict adverse obstetric and neonatal outcomes.

METHODS

We conducted a multicenter retrospective cohort study involving 9 regional perinatal centers in the United States. We examined the records of all monochorionic diamniotic twin pregnancies with two live fetuses at the 16- to 18-week sonographic examination who had serial follow-up sonography until delivery. The intertwin discordance in abdominal circumference, femur length, head circumference, and estimated fetal weight was calculated as the difference between the two fetuses, expressed as a percentage of the larger using the 16- to 18-week sonographic measurements. An adverse composite obstetric outcome was defined as the occurrence of 1 or more of the following in either fetus: intrauterine growth restriction, twin-twin transfusion syndrome, intrauterine fetal death, abnormal growth discordance (≥20% difference), and very preterm birth at or before 28 weeks. An adverse composite neonatal outcome was defined as the occurrence of 1 or more of the following: respiratory distress syndrome, any stage of intraventricular hemorrhage, 5-minute Apgar score less than 7, necrotizing enterocolitis, culture-proven early-onset sepsis, and neonatal death. Receiver operating characteristic and logistic regression-with-generalized estimating equation analyses were constructed.

RESULTS

Among the 177 monochorionic diamniotic twin pregnancies analyzed, intertwin abdominal circumference and estimated fetal weight discordances were only predictive of adverse composite obstetric outcomes (areas under the curve, 79% and 80%, respectively). Receiver operating characteristic curves showed that intertwin discordances in abdominal circumference, femur length, head circumference, and estimated fetal weight were not acceptable predictors of twin-twin transfusion syndrome or adverse neonatal outcomes.

CONCLUSIONS

In our cohort, only second-trimester abdominal circumference and estimated fetal weight discordances in monochorionic diamniotic twin pregnancies were predictive of adverse composite obstetric outcomes. Twin-twin transfusion syndrome and adverse neonatal outcomes were not predicted by any of the intertwin discordances measured.

Crown-rump length discordance and adverse perinatal outcome in twin pregnancies: systematic review and meta-analysis

OBJECTIVE

The aim of this systematic review was to explore the relationship between crown-rump length (CRL) discordance detected at 11-14 weeks of gestation and adverse outcome in twin pregnancy and to assess its predictive accuracy.

METHODS

A protocol designed a priori following MOOSE guidelines and recommended for systematic review and meta-analysis was used. The outcomes observed were: total fetal and perinatal loss, fetal loss at <24 weeks, fetal loss at ≥ 24 weeks, birth-weight (BW) discordance, preterm delivery (PTD) at < 34 weeks and fetal anomalies. The analysis was performed for all twins and for dichorionic (DC) and monochorionic (MC) twins separately.

RESULTS

A total of 2008 articles were identified and 17 studies were included in the systematic review. Twin pregnancies with CRL discordance ≥ 10% were at significantly higher risk of perinatal loss (RR, 2.80; 95% CI, 1.25-6.27; P = 0.012), fetal loss at ≥ 24 weeks (RR, 4.07; 95% CI, 1.47-11.23; P = 0.006), BW discordance (RR, 2.24; 95% CI, 1.89-2.64; P < 0.001) and PTD at < 34 weeks (RR, 1.49; 95% CI, 1.23-1.80; P < 0.001) but not of fetal loss at < 24 weeks (P = 0.130). A meta-analysis of fetal anomalies was not possible because fewer than two studies explored this outcome. However, when used alone to screen for adverse pregnancy outcome, the predictive accuracy of CRL discordance was low for each of the outcomes explored.

CONCLUSION

CRL discordance is associated with an increased risk of adverse pregnancy outcome. However, the accuracy of CRL discordance in predicting adverse outcome is poor and thus limits its routine use in clinical practice.