Fetal monitoring in pregnancies at and beyond 41 completed weeks: Prospective blind observational study of the use of umbilical and middle cerebral artery Doppler

Abstract

Objectives: To assess the association of umbilical and middle cerebral artery Doppler, with the need for medical intervention during labor and the occurrence of adverse neonatal outcome in pregnancies at/or beyond 41 weeks.

Methods: Prospective, observational study of all pregnant women at 41 weeks and beyond during one year in a single Maternity Unit. Doppler measurements of umbilical artery and middle cerebral artery resistance indices (UA-RI and MCA-RI) and cerebro placental ratio (CPR) were performed at 41 weeks, blinded to the clinical staff. Clinical management of prolonged pregnancy was based on routine antepartum fetal heart rate (FHR) monitoring and ultrasound assessment of oligohydramnios. The main outcome measures were 2 composite criteria: 1) "medical intervention during labor" including any of cesarean delivery for FHR abnormalities and/or need for fetal scalp blood sampling for lactate measurement; and 2) "suboptimal neonatal outcome" including any of 5-min Apgar score < 7, umbilical cord artery pH < 7.15, transfer to neonatal unit or perinatal death. The association between abnormal fetal Doppler and the outcome criteria was assessed.

Results: Out of 116 women recruited (12.3 % of all deliveries), 30 (25.9 %) had a medical intervention during labor and 16 (13.8 %) had a suboptimal neonatal outcome. None of antepartum FHR or oligohydramnios were associated with any of the primary outcomes. UA-RI and cerebro-placental ratio were strongly associated with the need for a medical intervention during labor (OR [95 % CI] 13.1 [1.4 - 122.2] and 5.1 [1.3 19.7], respectively) but not with the occurrence or a suboptimal neonatal outcome. If made available to the clinical staff, abnormal fetal Dopplers could have led to 12 additional inductions of labor and to the adequate identification of 13 interventions during labor including 6 cesareans for abnormal FHR.

Conclusion: Abnormal fetal Doppler beyond 41 weeks may help to better identify situations at risk for medical intervention for fetal concern during labor. Further studies are necessary to assess its prospective use for the management of prolonged pregnancies.

Keywords: Cerebral artery doppler; Cerebroplacental ratio; Prolonged pregnancy; Umbilical artery doppler; cesarean section; fetal heart rate.