Growth Velocity and Doppler Evaluation to Predict Nonreassuring Fetal Heart Rate at Birth in Low-Risk Women: A Prospective, Longitudinal Study

Introduction: This study investigated whether fetal growth deceleration in term, appropriate-for-gestational-age (AGA) fetuses is associated with placental insufficiency and nonreassuring fetal heart rate (NRFHR) at birth. Methods: In this prospective study, 246 low-risk, singleton pregnancies at term with AGA fetuses were recruited. Correlation between decreased growth velocity (decline in estimated fetal weight [EFW] percentile), low EFW (EFW[sup.Q1] = latest EFW between 11 and 25% percentiles), umbilical artery (UA) pulsatility index (PI), middle cerebral artery (MCA) PI, and cerebro-placental ratio (CPR) with cesarean and instrumental deliveries due to NRFHR were tested. Results: The median change between fetal weight estimates (percentiles/week) was +0.49% (95% CI: 4 to +5%). Ten percent had decreased EFW percentile >3.5%/week. Fetal growth velocity/week was associated with MCA (r = 0.21, p < 0.001) and CPR (r = 0.24, p < 0.001) and inversely correlated with UA PI (r = 0.28, p < 0.001). NRFHR and cesarean section (CS) rates due to NRFHR were associated with decreased growth velocity, EFW[sup.Q1], and low CPR. The combination of abnormal CPR with decreased growth velocity occurred in 12 pregnancies, of which 5 (42%) had urgent CS due to NRFHR. The combination of abnormal CPR with EFW[sup.Q1] occurred in 9 pregnancies, of which 4 (44%) had urgent CS due to NRFHR. These combinations increased the likelihood ratio of CS due to NRFHR two-fold (8.41; 2.54-24.5) but did not significantly alter the number needed to treat by elective CS (3.78-4.68). Conclusion: Fetal growth velocity, EFW between 10 and 25th percentiles (EFW[sup.Q1]), and abnormal CPR improves prediction of unplanned CS due to NRFHR among term AGA fetuses. This should be considered when counseling about the delivery method. Keywords: Appropriate for gestational age, Cerebro-placental ratio, Fetal growth deceleration, Fetal growth restriction, Growth trajectory, Small for gestational age