Clinical implications of crown-rump length discordance at 11-14 weeks in dichorionic twins.
Academic Article
Overview
abstract
BACKGROUND: Crown-rump length discordance, defined as ≥ 10% discordant, has been investigated as an early sonographic marker of subsequent growth abnormalities and is associated with an increased risk for fetal loss in twin gestations. Prior studies have not investigated the prevalence of fetal aneuploidy or structural anomalies in discordant twins or the independent association of crown-rump length discordance with adverse perinatal outcomes. Data are also limited on cell-free DNA screening for aneuploidy in discordant dichorionic twins. OBJECTIVE: To evaluate if crown-rump length discordance in dichorionic twins between 11-14 weeks gestation is associated with a higher risk of aneuploidy, structural anomalies, or adverse perinatal outcomes and to assess the performance of cfDNA screening in dichorionic twin pregnancies with crown-rump length discordance. STUDY DESIGN: This is a secondary analysis of a multicenter retrospective cohort study that evaluated the performance of cfDNA screening for the common trisomies in twin pregnancies from 12/2011-02/2020. For this secondary analysis, we included live dichorionic pregnancies with crown-rump length measurements between 11-14 weeks gestation. We compared twin pregnancies with discordant vs concordant crown-rump lengths and analyzed the prevalence of aneuploidy and fetal structural anomalies in either twin. Secondly, we compared the prevalence of a composite adverse perinatal outcome which included preterm birth <34 weeks, hypertensive disorders of pregnancy, stillbirth or miscarriage, small for gestational age birthweight, and birthweight discordance. We also 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 crown-rump length discordant vs concordant twins (9.9% vs 3.9% respectively, aRR 2.7 [95% CI 1.4-4.9]). Similarly, structural anomalies (aRR 2.5 [95% CI 1.4-4.4]) and composite adverse perinatal outcomes (aRR 1.2 [95% CI 1.04-1.3]) were significantly higher in discordant twins. A stratified analysis demonstrated that even without other ultrasound markers, there were increased risks of aneuploidy (aRR 3.5 95% CI 1.5-8.4) and structural anomalies (aRR 2.7 95% CI 1.5-4.8) in CRL discordant twins. Cell-free DNA screening had high negative predictive values for trisomy 21, trisomy 18, and trisomy 13, regardless of crown-rump length discordance, with one false-negative for trisomy 21 in a discordant twin pregnancy. CONCLUSIONS: Crown-rump length discordance in dichorionic twins is associated with an increased risk for 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, one false-negative result illustrates that there is a role for diagnostic testing. This 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.
