OP25.07: First trimester inter‐ and intrafetal size discrepancies in bichorionic twins conceived by in vitro fertilisation: can it predict pregnancy outcome?

Abstract

Early fetal growth restriction may predict adverse pregnancy outcome. We aimed to evaluate the association between first trimester inter- and intra-fetal size discrepancies to pregnancy outcome, among bichorionic-biamniotic twins conceived by in vitro fertilisation (IVF). Retrospective cohort analysis of all women with a first trimester bichorionic-biamniotic viable twin gestation, who conceived following IVF. Fetal size discrepancies were evaluated as either the gap between actual gestational age (GA) as calculated by ovum pick up (OPU) date to the evaluated GA determined by Crown–rump length (CRL) measurement for each twin or by CRL discrepancies between the twins. We analysed the association between fetal size discrepancies to pregnancy outcome. The primary outcome was the number of liveborn fetuses and the secondary outcomes included gestational age at birth, birthweight percentile and discorda. A total of 277 women were available for analysis. 218 (78.7%) women had a twin liveborn delivery, 41 (14.8%) had a singleton liveborn delivery and 19 (6.5%) had a non-liveborn pregnancy. Among the smaller than expected twins, the association between CRL-OPU differences to the primary outcome was significant for twin liveborn delivery (-1.43 day), singleton liveborn delivery (-4.12 days) and non-liveborn pregnancy (-6.72 days) (p<.001). For the largest twin the association is significant for non-liveborn pregnancy (-4.33 days) compared to any liveborn delivery, either singleton (-0.95 days) or twins (-0.21 days) (p<0.001). Among IVF conceived twin gestations, CRL-OPU gaps, is associated with fetal loss, of one or both twins.