The role of the cerebroplacental ratio in predicting pregnancy outcomes at 40-42 gestational weeks: a prospective observational trial.

PURPOSE: The cerebroplacental ratio is a sonographic tool used to predict poor pregnancy outcomes. Data are insufficient regarding its use in postdate pregnancy. We evaluated the cerebroplacental ratio's prediction of unfavorable pregnancy outcomes in women at 40-42 weeks gestation with normal amniotic fluid index.

METHODS: This prospective observational study included 101 women with low-risk singleton pregnancy and gestational age > 40 weeks who delivered in a university affiliated hospital during 2020-2021. The middle cerebral artery pulsatility index, the umbilical artery pulsatility index, and the cerebroplacental ratio, which is their quotient, were compared between women with favorable and unfavorable pregnancy outcomes. The latter included: meconium-stained amniotic fluid, cesarean or vacuum-assisted delivery due to pathological cardiotocography (category 2 or 3), 5-min Apgar score < 7, umbilical cord pH < 7.1, neonatal intensive care unit admission, and neonatal death.

RESULTS: Fetal Doppler, performed at a median gestational age of 40.3 (40.0-41.6), did not differ between 75 (74.3%) women with favorable obstetrical outcomes and 26 (25.7%) with unfavorable outcomes. In multivariate analysis, advanced maternal age and a history of a cesarean section were correlated with unfavorable outcomes, while Doppler indices were not found to be predictive. Among women at 41-42 weeks' gestation, for those with intrapartum fetal monitor category 2-3 vs. category 1, the mean umbilical artery pulsatility index was higher: 0.92 ± 0.34 vs. 0.71 ± 0.11 (p = 0.044).

CONCLUSION: According to the study results, fetal Doppler indices, including the cerebroplacental ratio, are not predictive of unfavorable outcome in women with pregnancies exceeding 40 weeks. Larger prospective studies are needed.