Re: Correlation between histological signs of placental underperfusion and perinatal morbidity in late-onset small-for-gestational-age fetuses. M. Parra-Saavedra,

In this study, the authors evaluate the presence of histological signs of underperfusion (PUP) in placental specimens from 126 late-onset small-for-gestational-age (SGA) fetuses with normal umbilical artery (UA) Doppler indices, finding an association between the existence of placental pathology and adverse neonatal outcome, as indicated by the morbidity assessment index for newborns. This work contributes to the ongoing debate regarding fetal hemodynamics and growth restriction (FGR) in the later weeks of pregnancy. Until recently, diagnosis in these fetuses pivoted exclusively on UA Doppler. Consequently, SGA fetuses with adequate UA impedance were considered genetically small. However, a proportion of these apparently normal fetuses suffered adverse outcome to varying degrees, especially when middle cerebral artery (MCA) Doppler anomalies were detected 1– 3 . Late-onset FGR has consequently emerged as a novel condition characterized by subtle chronic hypoxia, its diagnosis hinging typically, but not exclusively, on MCA Doppler. In addition, its pathophysiology is generally related more to a nutritional imbalance in-utero than to significant placental dysfunction causing abnormal umbilical impedance. Until now, the underlying cause of these hemodynamic disorders has not been defined clearly, and it is in this area that the study of Parra-Saavedra et al. really comes into its own, describing the existence of a variety of subtle pathological anomalies that are responsible for adverse outcome yet go undetected by UA Doppler examination.