In the expert review, Professor DeVore has evaluated the role of the cerebroplacental ratio (CPR) separately for early and late fetal growth restriction and risk pregnancies at term. The CPR by Doppler velocimetry was introduced more than 25 years ago. Comparable ratios have even been correlated with antenatal blood gases. Meanwhile, the CPR has experienced a renaissance in observational cohorts.

The strength of this review is the systematic and comprehensive approach. Although it is stated that the CPR is an earlier predictor than the Doppler indices of the middle cerebral artery (MCA) or umbilical artery (UA) alone, this is not directly compared in the tables.

In Figures 2–4, it is illustrated that a fetus near term may have pulsatility (PI) values of the UA and MCA within normal range, but a pathological CPR, reflecting the higher sensitivity of the ratio for adverse perinatal outcome. This is true for chronic placental perfusion diseases. However, there are patients with subacute or acute disturbances of oxygen diffusion in which the CPR may stay normal with a low resistance in the UA parallel to cerebral vasodilatation. This can be observed in patients with umbilical vessel thrombosis, gestational diabetes, or placental abruption in which the resistance in both vessels, the MCA and the UA, may even decrease, resulting in a normal CPR in spite of a high risk for fetal demise.

DeVore also states that the CPR is an earlier predictor of adverse outcome than the conventional biophysical profile score. However, the CPR can be part of a BPS as already described more than 20 years ago in fetuses with fetal growth restriction or postterm pregnancies when uterine Doppler and a CPR equivalent were integrated, leading to a better prediction of fetal distress and low Apgar values.

Although we appreciate the review, we would be cautious in emphasizing the value of an altered CPR as the sole predictor of adverse outcome as discussed. However, the correct timing of delivery remains crucial in improving long-term outcome of both mother and child. In addition, the impact of redistribution may be different at early as opposed to late gestation, and the CPR may not become clearly abnormal in case of acute events with sudden impaired oxygen diffusion.

Therefore, in spite of the convincing data on the value of the CPR, we should not forget the complex etiologies behind maternal and fetal hemodynamic profiles.