Prenatal life is recognised as a critical period where vital physiological processes may be permanently transformed leading to altered susceptibility to disease risk later in life.1 Accordingly, fetal adaptive responses to the maternal milieu, including the in utero effect of a physically active pregnancy, may influence the long-term health and well-being of the developing child. Is there potentially lifelong significance of maternal exercise on fetal health?

Although the recent study published in BJSM by Salvesen et al2 is timely with respect to the fetal response to extreme levels of maternal exertion in competitive Olympic hopefuls, it has limited applicability to the maternal population at large who are mostly inactive.3 The latter may benefit the most from a physically active, healthful pregnancy. In their study examining fetal response and utero-placental blood flow during strenuous treadmill running in the second trimester, Salvesen et al2 note that fetal HR was within the normal range as long as maternal exertion was below 90% maternal HRmax; an exercise intensity that few women would routinely work at, nor would be encouraged in a typical maternal population. If maternal HR exceeded 90% of maximum value and uterine artery blood flow was simultaneously less than 50% the initial value, fetal bradycardia occurred. However, despite these concerns, following exercise cessation fetal HR reached baseline values, uterine artery flow volume improved to resting values in most women and all birthweights were within the lower normal range for Norwegian children, which is encouraging.

Salvasen and …