The relationship between preeclampsia and intrauterine growth restriction in twin pregnancies.

Objective: Preeclampsia and intrauterine growth restriction (IUGR) are correlated in singleton pregnancies. The objective of this study was to estimate their relationship in twin pregnancies.

Study Design: Cohort of 578 patients with twin pregnancies delivered by 1 maternal fetal medicine practice from 2005-2013. Patients with chronic hypertension, monochorionic-monoamniotic placentation, twin-twin transfusion, and major congenital anomalies were excluded. Standard definitions were used for gestational hypertension and preeclampsia. We defined IUGR as any twin birthweight less than the 5th percentile for gestational age, as well as any twin birthweight less than the 10th percentile for gestational age.

Results: The incidence of preeclampsia was 14.9%, the incidence of birthweight <10% was 50.0%, and the incidence of birthweight <5% was 27.5%. Comparing patients with and without preeclampsia, the rate of birthweight <5th percentile did not differ (27.9% vs 27.4%, P = .929), nor did the rate of birthweight <10th percentile (48.8% vs 50.2%, P = .815). We had 80% power with an alpha error of 5% to show a difference in the likelihood of IUGR <10th percentile from 50% to 66% and a difference in the likelihood of IUGR <5th percentile from 27% to 42% in patients without and with preeclampsia.

Conclusion: In patients with twin pregnancy, there is no correlation between preeclampsia and IUGR. This suggests that in twin pregnancies, as opposed to singleton pregnancies, the pathophysiology may differ between these 2 common conditions.