Abnormal CPR or UCR reflect fetal cardiac output redistribution in favor of brain compared to placenta. They are shown to be useful in monitoring high-risk pregnancies, but longitudinal reference ranges of adequate sample size are lacking and gestational age related sex differences have not been examined. What are the clinical implications of this work? Longitudinal reference intervals of CPR and UCR were established which are more appropriate for serial monitoring of fetuses at risk of "brain sparing" due to placental insufficiency. Considering sex-differences may refine the the evaluation further.

ABSTRACT

Introduction. Centiles of middle cerebral artery pulsatility index and cerebroplacental ratio are useful for predicting adverse perinatal outcomes. A 'conditional centile' is conditioned by a previous measurement reflecting degree of individual change over time. Here we test whether such centiles are independent predictors and whether their combination improves prediction. Material and methods. This prospective longitudinal study included 220 pregnant women diagnosed with or at risk of having a small-for-gestational-age fetus. Serial Doppler measurements of the umbilical artery and middle cerebral artery pulsatility indexs were used to calculate cerebroplacental ratio. Preterm birth, operative delivery due to fetal distress, admission to neonatal intensive care unit, 5-min Apgar score <7, newborn hypoglycemia, and perinatal mortality were considered adverse outcomes. Possible associations were analyzed by logbinomial regression analysis. Results. Serial Doppler measurements of the middle cerebral artery were available in 207 participants and cerebroplacental ratio in 205. Conditional centiles ≤5 and ≤10 for both middle cerebral artery pulsatility index and cerebroplacental ratio were associated with increased risk for adverse perinatal outcomes. However, only the combination of cerebroplacental ratio centile and conditional centile ≤10 showed a better performance in the prediction of operative delivery due to fetal distress (p = 0.032), admission to neonatal intensive care unit (p = 0.048), and the combined variable "any adverse outcomes" (p = 0.034) compared with the use of centile ≤10 alone. Conclusions. Conditional centile for middle cerebral artery pulsatility index and cerebroplacental ratio ≤5 and ≤10 are associated with adverse perinatal outcomes. When adding conditional centile to conventional centile for cerebroplacental ratio, the prediction improved compared with the use of conventional centile alone.

The human yolk sac is involved in the regulation of embryonic growth, but contrary to our hypothesis, the yolk sac has a compensatory capacity, being larger when the mothers are smaller; and the effect can be traced on fetal size at 24 weeks of gestation.