Association between hypertensive disorders and fetal growth restriction in twin compared with singleton gestations

Hypertensive disorders of pregnancy (including preeclampsia or gestational hypertension) are associated with fetal growth restriction in singleton pregnancies, an association that may be attributed to abnormal placentation as the shared etiology between these conditions. Given that the pathogenesis of these conditions in twin pregnancies may involve mechanisms other than abnormal placentation, it is unclear whether a similar association between hypertensive disorders of pregnancy and fetal growth restriction is present in twins. Data on the relationship between hypertensive disorders of pregnancy and fetal growth restriction in twins are limited and conflicting. This controversy may be attributed to limitations of existing studies including the use of a singleton-based birthweight reference to define fetal growth restriction in twins and the lack of a positive control group of singleton gestations. The objective of the study was to determine the association between hypertensive disorders of pregnancy and fetal growth restriction in dichorionic twin gestations, using both a singleton- and a twin-based birthweight reference, and to compare this association with that observed in singleton gestations. We performed a retrospective cohort study of all women with dichorionic twin or singleton gestations giving birth in a single tertiary center during 2003–2015. Fetal growth restriction was defined in separate analyses as birthweight