Intrauterine Growth Restriction (IUGR) accounts for a significant proportion of perinatal morbidity and mortality currently encountered in obstetric practice. The primary goal of antenatal care is the early recognition of such conditions to allow treatment and optimization of both maternal and fetal outcomes. Management of pregnancies complicated by IUGR remains one of the greatest challenges in obstetrics. Frequently, however, clinical evidence of underlying uteroplacental dysfunction may only emerge at a late stage in the disease process. With advanced disease the only therapeutic intervention is delivery of the fetus and placenta. The cerebroplacental ratio (CPR) is gaining much interest as a useful tool in differentiating the "at risk" fetus in both IUGR and the appropriate for gestational age (AGA) setting. The CPR quantifies the redistribution of the cardiac output resulting in a brain sparing effect. The PORTO group, have previously demonstrated that the presence of a brain sparing effect is significantly associated with an adverse perinatal outcome in the IUGR cohort.
The aim of the PORTO Study was to evaluate the optimal management of fetuses with an estimated fetal weight <10th centile. The objective of this secondary analysis was to evaluate if normalizing CPR predicts adverse perinatal outcome.
1116 consecutive singleton pregnancies with IUGR completed the study protocol over 2 years at 7 centers, undergoing serial sonographic evaluation and multivessel Doppler measurement. CPR was calculated using the pulsatility and resistance indices of the middle cerebral and umbilical artery. Abnormal CPR was defined as <1.0. Adverse perinatal outcome was defined as a composite of intraventricular hemorrhage, periventricular leukomalacia, hypoxic ischemic encephalopathy, necrotizing enterocolitis, bronchopulmonary dysplasia, sepsis and death.
Data for CPR calculation was available in 881 cases, with a mean gestational age of 33 weeks (interquartile range, 28.7 -35.9). Of the 87 cases of abnormal serial CPR with an initial value <1.0, 52 % (n=45) of cases remained abnormal and 22% of these (n=10) had an adverse perinatal outcome. The remaining 48% (n=42) demonstrated normalizing CPR on serial sonography, and 5% of these (n=2) had an adverse perinatal outcome. Mean gestation at delivery was 33.4 weeks (n=45) in the continuing abnormal CPR group and 36.5 weeks (n=42) in the normalizing CPR group (p-value <0.001).
The PORTO group has previously demonstrated that the presence of a brain-sparing effect was significantly associated with an adverse perinatal outcome in our IUGR cohort. It had been hypothesized that a normalizing CPR ratio would be a further predictor of an adverse outcome due to the loss of this compensatory mechanism. However, in this sub-analysis we did not demonstrate an additional poor prognostic effect when the CPR value returned to a value >1.0. Overall, this secondary analysis has demonstrated the importance of a serial abnormal CPR value of <1 within the <34 weeks gestation population. Contrary to our proposed hypothesis, recognition that reversion of an abnormal CPR to a normal ratio is not associated with a heightened degree of adverse perinatal outcome.