Pregnancy and perinatal outcomes of first-trimester crown-rump length discordant IVF dichorionic twin pregnancies - a retrospective cohort study

Research Question: This study aimed to evaluate the association between discordance in crown-rump length (CRL) and adverse pregnancy and perinatal outcomes in dichorionic twin pregnancies. Design: This was a retrospective cohort study of dichorionic twin pregnancies after IVF that showed two live fetuses at the first ultrasound scan between 6 and 8 weeks gestational age from 1 January 2015 to 31 December 2016. Study groups were defined by the presence or absence of 20% or more discordance in CRL. The primary outcomes were early fetal loss of one or both fetuses before 12 weeks and birth-weight discordance. Secondary outcomes included fetal anomalies, fetal loss between 12 and 28 weeks, stillbirth, small for gestational age (SGA) at birth, low birthweight (LBW), very low birth-weight (VLBW), admission to the neonatal intensive care unit (NICU) and preterm delivery (PTD). Results: CRL-discordant twin pregnancies were more likely to end in the loss of one fetus before 12 weeks' gestation (odds ratio [OR] 15.877, 95% confidence interval [CI] 10.495-24.019). Discordant twin pregnancies with twin deliveries had a significantly higher risk of birthweight discordance (OR 1.943, 95% CI 1.032-3.989). There was no significant difference in perinatal outcomes including fetal anomalies, PTD, LBW, VLBW, SGA, neonatal death and admission to NICU between singleton or twin deliveries. Conclusions: Discordant twin pregnancies were at increased risk of one fetal loss prior to 12 weeks' gestation. Except for birthweight discordance, there was no significant difference between CRL discordance and other adverse perinatal outcomes.