Re: Risk of ultrasound-detected neonatal brain abnormalities in intrauterine growth-restricted fetuses born between 28 and 34 weeks' gestation: relationship with gestational age at birth and fetal Doppler parameters. R. Cruz-Martinez, V. Tenorio, N. Padil

Field: Medicine (Health Sciences)

Linked Comment: Ultrasound Obstet Gynecol 2015; 46: 452–459 Both prematurity and early-onset fetal growth restriction (FGR) have been associated with brain lesions and childhood neurocognitive dysfunction1, 2. This work compares their importance, proposing a protocol based on fetal hemodynamics to avoid neurological morbidity once the risk of fetal mortality has decreased. Importantly, the authors introduce two novel concepts: one is that fetal hemodynamics is more valuable than is gestational age for the prediction of cranial ultrasound anomalies; the second, and more crucial from a management perspective, is that, among the hemodynamic parameters, only those related to cerebral vasodilation, i.e. middle cerebral artery (MCA) and aortic isthmus (AoI) Doppler, yield information of relevance for the selection of fetuses prone to cranial ultrasound anomalies. This enables the authors to display a scenario in which prevention of brain damage pivots exclusively on cerebral impedance, while vasodilation is not a protection mechanism but the channel by which the fetal brain heralds the existence of compromise. As indicated by the authors, once the risk of fetal mortality decreases, efforts should focus on prevention of brain damage. In this regard, although the appropriate management protocol remains to be established, this work contributes sufficient information to allow construction of an initial approach. If half of the fetuses with abnormal MCA Doppler present with cranial ultrasound anomalies, and this percentage increases to two thirds when there is reversed AoI flow, then quantification of cerebral impedance may be of potential value in the avoidance of neurocognitive dysfunction. Cerebral flow and its ratio with that of the umbilical artery, the cerebroplacental ratio (CPR), are becoming an increasing source of information for the evaluation of fetal health3, showing at term a higher correlation with adverse outcome than does birth weight (BW)4. Unfortunately, the authors did not study CPR and BW, but it is likely that comparing them would produce similar results, the association of cranial ultrasound anomalies with CPR being stronger than the association with prematurity or BW. However, this remains to be evaluated in future work. Finally, it is also noteworthy to mention that about 40% of the lesions observed just after birth were not present prenatally at 40 weeks. Interestingly, MCA Doppler seemed to discriminate more significantly in the case of early lesions, while AoI Doppler performed better in the case of late cranial ultrasound anomalies. But why? If we aim to design a useful protocol to avoid brain damage in early-onset FGR, the meaning of these findings needs to be further clarified; we need to determine the percentage of cases with true neurocognitive dysfunction in the long term, and its relationship with the abovementioned Doppler parameters. In summary, this paper contributes key research and is a starting point in the development of an accepted protocol for the prevention of brain damage in early-onset FGR.