Association between first-trimester uterine artery Doppler and crown-rump length with growth discordance: does it make a difference

OBJECTIVES

The purpose of this study was to investigate the association between first-trimester uterine artery pulsatility index (UtA-PI) and crown-rump length discordance (CRLD) with growth discordance (GD) in twins and analyze the influence of chorionicity in these parameters.

METHODS

This retrospective analysis integrated data from the twin pregnancy database of Centro Hospitalar São João (2019-2023), including 184 fetuses, with 19 monochorionic and 73 dichorionic gestations. To determine the association between UtA-PI and CRLD with GD, correlation analyses were computed and linear regression models were carried out. Separate analyses were conducted for each type of placentation. Logistic regression analysis was carried out to determine the association of mean UtA-PI and CRLD with severe GD, defined as discordance ≥25 %.

RESULTS

GD≥25 % was detected in 9.80 % of pregnancies. A statistically significant difference between monochorionic and dichorionic gestations was found in crown-rump length (p=0.009), CRLD (p<0.001) and birth weight (p=0.025), but not in mean UtA-PI (p=0.853) or GD (p=0.556). Mean UtA-PI was significantly higher in discordant than in concordant pairs (p<0.001), but that association was not seen in CRLD (p=0.931). Mean UtA-PI and GD were correlated by the regression line "GD=3.844 × UtA-PI + 6.638", with R2 0.027. CRLD and GD were correlated by the regression line "GD=0.280 × CRLD + 10.79", with R2 0.010. Mean UtA-PI, but not CRLD, was significantly associated with severe GD (odds ratio, 22.753; p=0.002).

CONCLUSIONS

Mean UtA-PI, but not CRLD, is associated with GD. The prevalence of severe GD increases significantly with increasing mean UtA-PI.

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.

Physical growth and intelligence development of discordant dizygotic twins from birth to preschool age: a prospective cohort study

Background

The majority of studies are limited to adverse perinatal outcomes and poor cognitive abilities in the short term in discordant monochorionic twins.

Methods

To determine whether small and large discordant dizygotic twins differ in physical growth and intelligence development and weight and height from birth up to 6 years of age were measured in 34 dizygotic twin pairs with ≥ 20% birth weight discordance. Mental developmental index (MDI) and psychomotor developmental index (PDI) were calculated at 1 year, while the Wechsler Intelligence Scale for Children-IV (WISC-IV) full-scale intelligence quotient (IQ) was assessed at the age of 6.

Results

The difference in height and weight in each stage differed significantly from birth to 72-months-old (P < 0.05), although there was disappointing catch-up growth in smaller twins. PDI but not MDI at 1 year of age was significantly different between the two groups (P < 0.05), and smaller twins experienced higher psychomotor retardation rates (P < 0.05). Also, the influence of height and weight on PDI was statistically significant (P < 0.05). No significant difference was detected in the WISC-IV full-scale IQ at the age of 6; however, the full-scale IQ may be affected by the history of suffocation and the S/D value (P = 0.011, P = 0.022).

Conclusions

Intrauterine fetal growth and development lead to birth weight differences in twins and sustain an impact on the children’s physical growth in height and weight from birth to preschool age, causing psychomotor developmental differences at 1 year of age. However, the differences in psychomotor development decrease gradually by the age of 6.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-022-01354-y.

Assessment of different thresholds of birthweight discordance for early neonatal outcomes: retrospective analysis of 2348 twin pregnancies

Background

The optimal threshold of birthweight discordance (BWD) remains controversial. This study aimed to evaluate the associations between BWD at different thresholds and early neonatal outcomes and to assess their predictive accuracy.

Methods

This was a retrospective cohort study using a birthweight data with the chorionicity information of 2348 liveborn twin pairs at a gestational age of ≥26 weeks, from 2012 to 2018. The percentage of BWD was calculated by dividing the actual birthweight difference by the weight of the larger twin and multiplying by 100. Outcomes of interest included neonatal intensive care unit (NICU) admission, neonatal respiratory distress syndrome (NRDS), ventilator support and a composite outcome combining major morbidities and neonatal death. Logistic regression models were performed to estimate the association between neonatal outcomes and BWD with different thresholds (≥15.0%, ≥20.0%, ≥25% and ≥ 30%). Generalized estimated equation (GEE) models were used to address intertwin correlation. Restrictive cubic spline (RCS) models were established to draw the dose-response relationship between BWD and the odds ratios of outcomes. Clustered receiver operating characteristic (ROC) curve analyses were performed to assess the predictive accuracy.

Results

Of 2348 twin pairs, including 1946 dichorionic twin pairs and 402 monochorionic twin pairs, BWD was significantly associated with NICU admission, regardless of the thresholds used. The incidence of NRDS, ventilator support and the composite outcome were significantly higher when a threshold of ≥20% or greater was chosen. The dose-response relationship showed nonlinear growth in the risk of adverse neonatal outcomes with increasing BWD. ROC analyses showed a low significant AUROC of 0.569 (95% CI: 0.526–0.612) for predicting NICU admission but no significant AUROCs for predicting other outcomes. A BWD of ≥30% provided a moderate increase in the likelihood of NICU admission [positive likelihood ratio (LR⁺) = 5.77].

Conclusion

Although BWD is independently associated with adverse neonatal outcomes, it is not a single predictor for neonatal outcomes given the weak discriminative ability to predict neonatal outcomes. A cutoff of 30% is more practical for risk stratification among twin gestations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04417-4.

Ultrasound in the prediction of birthweight discordance in dichorionic twins

INTRODUCTION

Large birthweight discrepancy has been identified as a risk factor for perinatal morbidity and mortality in twin pregnancies. However, it remains unclear whether such discordance can be predicted by various biological indices with specific cut-off values, and how these depend on the gestational age. We aimed to determine the most effective way to predict large birthweight discordance at various gestational ages.

MATERIAL AND METHODS

A retrospective cohort study of dichorionic twins, live-born between 2008 and 2018, was conducted. Discordances in biparietal diameter, head circumference, humerus and femur length, abdominal circumference, and estimated fetal weight were calculated-([larger twin - smaller twin] / larger twin) × 100%-and compared between those with and without a large birthweight discordance (≥20%). Receiver operating characteristic curves were constructed to analyze the predictive characteristics of each parameter.

RESULTS

Of 598 dichorionic twin pregnancies included, 83 (13.9%) had a birthweight discordance ≥20%. Group differences in biparietal diameter and head circumference discordance were the earliest to emerge (before 20 weeks of gestation), but became insignificant after 36 weeks, followed by humerus and femur length, estimated fetal weight discordance (after 20 weeks), and abdominal circumference discordance (after 28 weeks). The best predictors (with cut-off values) were discordance in biparietal diameter ≥7.8% at <20 weeks, head circumference ≥4.5% at 20-23⁺⁶  weeks, humerus length ≥4.5% at 24-27⁺⁶  weeks, and estimated fetal weight discordance (≥11.6% at 28-31⁺⁶  weeks, ≥10.5% at 32-35⁺⁶  weeks, and ≥15.0% ≥36 weeks), with sensitivity and specificity of 52%-77% and 69%-82%, respectively.

CONCLUSIONS

Different predictors and cut-off values may be useful for predicting large inter-twin birthweight discordance in dichorionic twins at different gestational ages. It is more accurate to use biparietal diameter and head circumference discordance in the early second trimester, humerus length discordance in the late second trimester, and estimated fetal weight discordance in the third trimester.

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.

Abdominal circumference discordance for prediction of small for gestational age at birth in twin pregnancies

OBJECTIVE

To evaluate whether single sonographic abdominal circumference (AC) discordancy estimation can predict small for gestational age (SGA) at birth in twin gestations.

METHODS

A retrospective analysis of prospectively collected data. Cohort included all twin gestations delivered at one university-affiliated medical center between 2010 and 2018, with available sonographic evaluation from 22 gestational weeks to term. Pregnancies complicated by fetal chromosomal abnormalities, major anomalies or twin to twin transfusion syndrome were excluded. One sonographic evaluation per pregnancy was selected randomly. AC discordance was calculated as (large twin AC - small twin AC)/large twin AC*100. Prediction of SGA at birth for at least one newborn (<10% percentile for gestational age by gender-specific local curves for multiples) was evaluated using ROC statistics with calculation of Youden index to establish best AC discordance cutoff. AC discordance prediction performance was compared to estimated fetal weight discordance performance. Results were adjusted for confounders using logistic regression analysis.

RESULTS

After exclusion, 236 twin gestations entered analysis. Of them, 200/236 (84.7%) were dichorionic-diamniotic twins. Mean gestational age at ultrasound evaluation and at delivery were 30.9 ± 4.4 and 35.9 ± 2.4 weeks, respectively. In 28/236 (11.8%) pregnancies, at least one neonate was born SGA. AC discordance predicted SGA at birth as good as sonographic estimated fetal weight (sEFW) discordance: ROC-AUC 0.76, 95% CI 0.67-0.85 vs. 0.77 95% CI 0.66-0.87, p < .001 for all. Best AC discordance cutoff for prediction of SGA at birth was 7.1% (57% sensitivity, 87% specificity), ROC-AUC 0.72 (95% CI 0.61-0.84, p < .001). Results remained significant after adjustment for maternal age, nulliparity, chorionicity and ultrasound to delivery interval (aOR 1.21 95% CI 1.1-1.32, p < .001).

CONCLUSION

According to our results, AC discordance at single sonographic evaluation can predict SGA at birth in twin gestations as good as sEFW discordance. Best cutoff for SGA prediction was 7.1%.

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.

Placental T2* estimated by magnetic resonance imaging and fetal weight estimated by ultrasound in the prediction of birthweight differences in dichorionic twin pairs

INTRODUCTION

Intertwin birthweight (BW) difference is associated with an increased risk of adverse outcome. Ultrasound estimated fetal weight (EFW) is the current method to predict intertwin BW difference, however, the sensitivity is poor. Therefore, new methods are needed. Placental T2* estimated by magnetic resonance imaging (MRI) provides non-invasive information about the placental function. This study aimed to investigate placental T2* difference as a new predictor of BW difference, and to compare it to the EFW.

METHODS

We included 25 dichorionic twin pairs at 19-38 weeks' gestation. Placental T2* was obtained by MRI and EFW by ultrasound. Correlations between each predictor and BW difference were examined by simple linear regression, and the combined model was analyzed by multiple linear regression and likelihood ratio test.

RESULTS

Strong positive correlations were demonstrated between intertwin differences in placental T2* and BW (r = 0.80, p < 0.005), and EFW and BW (r = 0.64, p < 0.005). Placental T2* difference was a strong independent predictor of BW difference (p < 0.001), and the combined model performed better than each predictor alone (p < 0.0001).

DISCUSSION

This pilot study demonstrates that placental T2* difference may be a predictor of intertwin BW difference irrespectively of fetal size. The clinical potential of this method deserves further investigation in a larger clinical study.

The value of ultrasound in predicting isolated inter-twin discordance and adverse perinatal outcomes

PURPOSE

To investigate the value of ultrasound approaching delivery to predict isolated inter-twin discordance and adverse perinatal outcomes.

METHODS

We retrospectively included twin pregnancies with sonography approaching delivery in ten maternal-foetal medicine centres in China from 2013 to 2014. Estimated foetal weight (EFW) and inter-twin EFW disparity (EFWD) were calculated based on biometry parameters. Percentage errors between EFW and actual birthweight or between EFWD and actual inter-twin disparity were calculated. ROC curves and multiple logistic regression were applied to evaluate the ability of EFWD to predict inter-twin disparity ≥ 25%, stillbirth, asphyxia and admission to a neonatal intensive unit (NICU). Chorionicity-stratified analysis was further performed.

RESULTS

Two hundred sixty-six monochorionic and 760 dichorionic twin pregnancies were analysed. The percentage errors in foetal weight estimations were 7-13%, whereas percentage errors in the estimation of inter-twin disparity were nearly 100%. Among eight formulas, Hadlock1 performed best, with a detectable rate of 65% and a false positive rate of 5% when predicting inter-twin disparity ≥ 25%. EFWD ≥ 22% was strongly associated with stillbirth (OR = 4.17, 95% CI 1.40-12.40) and NICU admission (OR = 3.48, 95% CI 2.03-5.97) after adjustment for gestational age, parity and abnormal umbilical systolic/diastolic ratio. Ultrasound had better predictive ability in monochorionic twins.

CONCLUSION

The predictive value of ultrasound for isolated inter-twin discordance and adverse perinatal outcomes was limited, which was possibly due to the magnifying of systematic errors in the disparity estimation compared with weight estimation. Despite this, abnormal biometry was an independent contributor for the poor prognosis of neonates.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

The role of ultrasound in the prediction of birth weight discordance in twin pregnancies: are we there yet?

OBJECTIVE

To analyze the accuracy of ultrasound prediction of birth weight discordance (BWD) and the influence of chorionicity and fetal growth restriction (FGR) on ultrasound performance.

METHODS

Retrospective analysis of 176 twin pregnancies at a Portuguese tertiary center, between 2008 and 2014. Last ultrasound biometry was recorded. Cases with delivery before 24 weeks, fetal malformations, interval between last ultrasound and deliver >3 weeks, twin-to-twin transfusion syndrome and monoamniotic pregnancies were excluded. The accuracy of prediction of BWD was assessed using the area under the receiver-operating characteristics curve (AUC).

RESULTS

BWD ≥20% was present in 21.6% of twin pregnancies. EBW had the best predictive performance for BWD (AUC 0.838, 95%CI 0.760-0.916), with a negative predictive value of 86.9% and a positive predictive value of 51.3%. Chorionicity did not influence ultrasound performance. None of the biometric variables analyzed was predictive of BWD in pregnancies without FGR.

CONCLUSION

The accuracy of ultrasound in the prediction of BWD is limited, particularly in pregnancies without fetal growth restriction. Clinical decisions should not rely on BWD alone.

Ethical considerations in the care of complicated twin pregnancies

Twin gestations are increasing in prevalence worldwide, and are potentially subject to medical complications which present uniquely complex ethical and psychosocial challenges for the pregnant patient and obstetrician to navigate. In this article, we explore these issues as they relate to medical decision-making in cases of discordant growth and discordant anomalies in both monochorionic and dichorionic twin pregnancies, including those affected by twin-twin transfusion syndrome, with particular attention to scenarios in which the individual fetuses hold competing interests. For each of these scenarios, we consider how decisions may positively or negatively impact one or both fetuses, and how familiarity with population outcomes, as well as sensitivity to the complex psychosocial circumstances surrounding these pregnancies, can support and inform shared decision-making.

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.

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.