The Prospective Observational Trial to Optimize Pediatric Health in IUGR (PORTO) study challenges the idea that Doppler interrogation of intrauterine growth-restricted (IUGR) fetuses might be useful to describe a sequence of cardiovascular adaptation. In my opinion, these findings need to be put into a gestational age perspective.

The Trial of Umbilical and Fetal Flow in Europe (TRUFFLE) study and other studies on severe IUGR recruited IUGR fetuses at <32 weeks of gestation (average gestation at delivery, 30.7 weeks); all fetuses had an abnormal umbilical artery (UA), inclusion criteria, and uterine artery Doppler velocimetry. These 3 conditions attest to the severity of IUGR. Hence, the sequence of Doppler events that represent progressive cardiovascular adaptation to placental insufficiency that was seen in the TRUFFLE study applies specifically to these conditions: severe, early-onset, placental insufficiency. Preferential shunting of umbilical venous blood straight to the heart through the ductus venosus (DV) is a preterminal event under the latter conditions and seldom, if ever, occurs at >34 weeks of gestation.

In the PORTO study, only 46% of the IUGR fetuses had an abnormal UA pulsatility index (PI); the mean gestational age at enrollment to the study was 30.1 weeks, but the mean gestational age at delivery was 37.8 weeks. With late IUGR near term and with normal umbilical PI, the best predictor of fetal adaptation to hypoxemia is the middle cerebral arteries (MCA) PI. Under these circumstances, only the MCA/UA (cerebroplacental) ratio may be of value in assessing fetal and neonatal risks. If Doppler interrogation is put into a gestational perspective, it is obvious that this cohort of late IUGR, abnormal UA, and MCA Doppler velocimetry remain the strongest predictors of adverse outcome. However, it is important to acknowledge that this statement misses its point when deprived of its time domain.

Unfortunately, in the PORTO study, the criteria for delivery differed among centers and staff members. This might bring in relevant observational bias in sequential observations, especially with severe early-onset IUGR. Similarly, I have concerns over what the PORTO investigators interpreted as an abnormal DV. In our experience and apparently in the TRUFFLE study centers, there is no single case of an abnormal DV Doppler velocimetry that persisted for 37 days without being censored by an abnormal low short-term variability at computerized cardiotocography within a matter of a few days. The main problem in understanding the bulk of the PORTO longitudinal observations is that, despite the statement “no statistical differences in the evolution of the main six patterns,” no information is presented on gestational age and birthweight of the different “patterns” and their outcome.

I sincerely hope that, in the future research outputs of the PORTO group, the language of elegant longitudinal investigation of late IUGR might be translated into the realm of fetal physiologic condition along gestation. Without this approach to the PORTO data, clinicians might be induced to think that 60 years of scientific advancements in the field of human fetal physiology are closed and forgotten in the drawers of history.