OP21.03: The role of CRL discrepancy in prediction of outcome in dichorionic twin pregnancy after IVF conception

Abstract

To assess whether the intertwin discrepancy in crown–rump length (CRL) between two twins at 11+0 to 13+6 weeks of gestation, is predictive of poor pregnancy outcome in IFV pregnancy with known date of embryo transfer and known gestational age (GA). This was a retrospective analysis of data collected prospectively over 2 years. Women with dichorionic twin pregnancy after IVF were scanned at 11+0 to 13+6 weeks of pregnancy. Women with monochorionic twin pregnancy were excluded from the study because CRL discrepancy in those twins could be a sign of early TTTS. The CRL ratio between the two fetuses was calculated. CRL-based GA and actual GA were compared. The distribution of discrepancies was analyzed according to pregnancy outcome. A total of 104 twin pregnancies were included. The discrepancy in CRL was expressed as a percentage of the CRL of the larger twin. The 95(th) and 99(th) centile for CRL discrepancy in twins was 13,7% and 28,9%, respectively. In 6/104 twin pairs the CRL discrepancy was larger than 95(th) centile. In all these cases the measured CRL of the bigger twin was closer to the actual GA. In 5 of these cases poor pregnancy outcome was observed for smaller twin (2 cases of chromosomal abnormality, 1 fetal demise and 2 severe fetal IUGR resulting in neonatal death). In twins with discrepancy less than 95(th) centile there were no cases with poor outcome for smaller twin and no cases with IUGR of twin with smaller CRL later in pregnancy. CRL discrepancy in dichorionic twin pregnancies in the first trimester occurs quite frequently. Discrepancy>95th centile indicates major growth delay and may indicate the presence of aneuploidy or could result in severe IUGR with poor outcome. In IVF pregnancies with CRL discordance the CRL of the bigger twin is more accurate in estimation of the actual GA.