Risk factors for Cesarean delivery in pregnancies with a small‐for‐gestational‐age fetus undergoing induction of labor

OBJECTIVE: To identify risk factors for cesarean delivery in small-for-gestational age (SGA) fetuses undergoing induction of labor. METHOD: This was a retrospective cohort study of non-anomalous, singleton gestations delivered in a single tertiary referral center who met criteria for SGA, defined as an estimated fetal weight (EFW) less than 10th percentile. Our primary outcome was to identify risk factors associated with cesarean delivery in pregnancies complicated by SGA and undergoing induction of labor. The secondary outcome was to identify risk factors associated with non-reassuring fetal heart tracing (NRFHT). Univariate and multivariable analyses were used to determine which clinical characteristics, available at the time of admission, were most associated with cesarean delivery during labor induction. The predictive value of the final model was assessed with the area under the receiver operator curve (AUC). Sensitivity and specificity of the model were also assessed. Internal validation of the model was performed using 10,000 bootstrap replicates of the original cohort. The adequacy of the model was evaluated using the Hosmer-Lemeshow goodness-of-fit test. RESULTS: Cesarean delivery occurred in 243 (40.9%) pregnancies. Significant risk factors associated with cesarean delivery and included in the final model were maternal age, gestational age at delivery, and initial method of labor induction. The bootstrap estimate of the AUC of the final prediction model was 0.82 (95% confidence interval (CI) 0.78 - 0.86). The model had a sensitivity of 64.2%, specificity of 86.9%, positive likelihood ratio (LR) of 4.9, and negative LR of 0.41 for cesarean delivery. The model had a good fit (p = 0.617). NRFHT complicated 117 (19.7%) pregnancies. Significant risk factors for NRFHT included EFW less than 5th percentile, abnormal umbilical artery Doppler studies (pulsatility index > 95th percentile or absent / reversed end-diastolic flow), and gestational age at delivery. CONCLUSION: We identified several significant risk factors for cesarean delivery and NRFHT among SGA fetuses undergoing induction of labor. Clinicians may use these risk factors to guide patient counseling and to help anticipate the potential need for operative delivery. This article is protected by copyright. All rights reserved.