Objectives: The cerebroplacental ratio (CPR) represents the relationship between blood flow in the placenta and blood flow in the fetal brain. A low CPR in the third trimester has been associated with poor perinatal outcomes in both singleton and twin gestations. This study aimed to evaluate whether low CPR defined or high CPR discordance at 20-24 weeks in twin pregnancies is associated with an increased risk of fetal growth restriction (FGR) in the third trimester.
Methods: A total of 247 twin pregnancies were included in this retrospective cohort study. Monoamniotic monochorionic twins were excluded. An abnormal CPR was defined as one or both CPR <5%-ile or CPR discordance between fetuses >20%. FGR was evaluated using the last growth measurement performed between 28 and 36 weeks.
Results: Of the candidates for study, 177 twin pregnancies had normal CPRs and 70 twin pregnancies had abnormal CPRs. Maternal demographics were similar between groups. There was no difference in the risk of selective FGR, FGR of both twins, or growth discordance >20% in the third trimester between twin pregnancies with normal vs. abnormal CPRs at 20-24 weeks. The adjusted odds ratio for any growth disturbance was 1.00 (95% CI 0.56-1.79).
Conclusions: This study suggests that FGR in twins may be the consequence of numerous maternal, fetal, and placental factors, and not fully explained by redistribution of blood flow or adaptive hypoxia in the mid-trimester.
Keywords: Cerebroplacental ratio; fetal blood flow; fetal growth restriction; twins; uteroplacental Doppler.