Role of cerebroplacental ratio for fetal assessment in prolonged pregnancy

Objective The aim of this study was to assess the role of the cerebroplacental ratio (CPR), i.e. the ratio between the middle cerebral artery and umbilical artery pulsatility indices, in detecting fetal compromise in prolonged pregnancy. Methods Women attending a dedicated postdates clinic at 41 weeks' gestation were recruited for the study and CPR was calculated at 41+3 weeks. Induction of labor was offered at 42 weeks to those women still undelivered. Unfavorable outcome was defined as cord arterial pH < 7.15 with a base deficit of > 11 mM/L or operative delivery for abnormal intrapartum fetal electrocardiogram ST-segment analysis. The 5th centiles of the CPR, obtained from published reference ranges (0.90) and from our population (0.98), were used as lower cut-off values. Results Three hundred and twenty women who reached a gestational age of over 41 weeks were eligible for inclusion in the study. The median gestational age at delivery was 294 (range, 289-300) days. Unfavorable outcome was observed in 58/320 pregnancies. There was no significant difference in the proportion of unfavorable outcomes between the two groups defined using either CPR cut-off value (both P > 0.05). Conclusion CPR is not predictive of unfavorable outcome in women with pregnancies lasting more than 41 weeks. Copyright © 2012 ISUOG. Published by John Wiley & Sons Ltd.