The relationship between intrapartum cerebroplacental ratio and adverse perinatal outcomes in term fetuses.

OBJECTIVES

The cerebroplacental ratio (CPR) Doppler has been proposed as an instrument for predicting adverse perinatal outcomes particularly during antepartum period. Abnormal CPR is associated with non-reassuring fetal status requiring operative delivery, low Apgar score and neonatal complications. The aim of this study was to assess the role of CPR Doppler in the labor triage suite, so as to identify fetuses at risk for non-reassuring status as well as other adverse perinatal outcomes.

METHODS

This was a prospective cohort study of term pregnancies who attended the labor room during the latent phase of labor. Both fetal Middle Cerebral Artery Pulsatility Index (MCA-PI) and Umbilical Artery Pulsatility Index (UA-PI) were measured and these values were converted to CPR values. Non-reassuring fetal status requiring operative delivery and other adverse perinatal outcomes were compared between women with normal and abnormal CPR values. Accuracy of CPR for predicting non-reassuring fetal status and abnormal fetal heart rate patterns were calculated.

RESULTS

A total of 384 women were recruited. Lower CPR values were observed in women who underwent operative delivery for non-reassuring fetal status. However, when dividing women into normal and abnormal CPR groups, using 3 different cut-off values, the rate of non-reassuring fetal status was not significantly different between the groups. There was a significantly higher rate of abnormal fetal heart rate monitoring in fetuses with CPR < 5 percentile and CPR < 1. CPR appeared to have a low positive predictive value (PPV) for predicting non-reassuring fetal heart rate patterns, however, the negative predictive value (NPV) was high.

CONCLUSIONS

In term fetuses, lower CPR is associated with non-reassuring fetal status. CPR measurement during the intrapartum period with currently available CPR cut-off values is not a good predictor for adverse perinatal outcomes, with the exception of abnormal fetal heart rate patterns. However, the high NPV may be used to stratify pregnant women who may benefit from continuous fetal heart rate monitoring.