Prelabor screening for intrapartum fetal compromise in low‐risk pregnancies at term: cerebroplacental ratio and placental growth factor

We sought to determine the screening performance of a low fetal cerebroplacental ratio (a marker of fetal adaptation to suboptimal growth) and maternal placental growth factor levels, respectively, both in isolation and in combination, for the detection of cesarean section for intrapartum fetal compromise and serious composite neonatal outcome. A prospective cohort study was performed on low risk women with uncomplicated singleton pregnancies from 36 weeks to delivery. Fortnightly assessment of the cerebroplacental ratio and placental growth factor was performed and intrapartum and neonatal outcomes were recorded. Values from the final assessment for each woman were corrected for gestation and assessed for screening performance, firstly as continuous variables and then as binary predictors. Of the 264 women who consented to participate in the study, 207 were included in the final analysis. Babies born by cesarean section for intrapartum fetal compromise had lower cerebroplacental ratio and placental growth factor centiles than all other deliveries. Women with babies born with the serious composite neonatal outcome had lower placental growth factor centiles. The highest Area under the Receiver Operative Characteristic Curve for cesarean section for intrapartum fetal compromise (0.92, 95% CI 0.86-0.97) and serious composite neonatal outcome (0.64, 95% CI 0.54-0.74) was achieved by a combination of the cerebroplacental ratio 20th and placental growth factor 33rd centiles respectively. This produced sensitivities, specificities and positive likelihood ratios for cesarean section for intrapartum fetal compromise and serious composite neonatal outcome of 100%, 86%, and 7.14, and 34.2%, 87.0%, and 2.63, respectively. There was no statistical difference in the Area under the Receiver Operative Characteristic Curve between the combined model and the cerebroplacental ratio alone for cesarean section for intrapartum fetal compromise nor the combined model and the cerebroplacental ratio or placental growth factor in isolation for adverse neonatal outcome. This pilot, proof of principle study describes the screening performance for detection of cesarean section for intrapartum fetal compromise in low risk women from 36 weeks gestation using the fetal cerebroplacental ratio and maternal placental growth factor levels. We found that the cerebroplacental ratio and maternal placental growth factor improved the overall predictive utility for cesarean section for intrapartum fetal compromise and adverse neonatal outcome. However, given the lack of significant difference between the combined model and its individual components it is debatable that the combined model is a superior screening test.