Prediction of adverse perinatal outcome by cerebroplacental ratio adjusted for estimated fetal weight

OBJECTIVES: To evaluate the relationship between cerebroplacental ratio (CPR) and estimated fetal weight (EFW) in low- and high-risk singleton pregnancies. Furthermore, we evaluated the role of CPR in the prediction of adverse perinatal outcome and whether CPR measurements adjusted for EFW improve its predictive value.

METHODS: This was a retrospective cohort study including pregnancies in which Doppler investigations of umbilical artery (UA) and fetal middle cerebral artery (MCA) were performed at ≥ 30 weeks' gestation. Pregnancies were allocated to one of three groups according to EFW centile: small-for-gestational age (SGA) with EFW < 10th centile, appropriate-for-gestational age (AGA) and large-for-gestational age (LGA) with EFW > 90th centile. CPR was calculated as the ratio between the UA pulsatility index (PI) and MCA-PI and converted to CPR multiples of the median (MoMs) according to the three EFW groups. Linear regression analysis was performed to evaluate the relationship between CPR-MoMs and EFW centiles in low-risk pregnancies. Furthermore, MoMs of CPR adjusted according to EFW centile (aCPR-MoMs) were calculated. Adverse perinatal outcome was defined as presence of pathological cardiotocography (CTG) trace, arterial cord blood pH < 7.1, 5-min Apgar score < 7 and presence of meconium-stained amniotic fluid (MSAF).

RESULTS: A total of 3515 (3016 low risk and 499 high risk) pregnancies, delivered between January 2010 and March 2016, were included. Linear regression analysis revealed a significant positive correlation between EFW centile and CPR-MoM. Receiver-operating characteristics (ROC) curve analysis showed a significant association between CPR-MoM and pathological CTG trace (AUC, 0.539; SD, 0.014; P = 0.005) and low Apgar score (AUC, 0.609; SD, 0.041; P = 0.008), but not with low arterial pH or MSAF. There was a significant association between aCPR-MoM and pathological CTG trace (AUC, 0.540; SD, 0.014; P = 0.003), low arterial cord blood pH (AUC, 0.546; SD, 0.022; P = 0.035) and low Apgar score (AUC, 0.609; SD, 0.044; P = 0.008), but not with MSAF. However, detection rates for adverse perinatal outcomes by CPR-MoM and aCPR-MoM were low, ranging from 6.7% to 28.6% for SGA, 12.1% to 22.2% for AGA and 0% to 33.3% for LGA, for a false-positive rate of 10%. In a subgroup analysis of cases in which ultrasound examination was performed at ≥ 34 weeks of gestation and within 4 weeks of delivery (n = 1439), the ROC curves for aCPR-MoM were significantly associated with all four outcomes evaluated.

CONCLUSIONS: CPR-MoM values are dependent on EFW centiles; therefore, we suggest that CPR-MoM should be adjusted for EFW centile. However, both CPR- and aCPR-MoM showed a low prediction rate for adverse perinatal outcome. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.