The acute effects of exercise on fetal well‐being in pregnancies complicated by fetal growth restriction with normal Dopplers: A prospective study

Abstract Background The potential risks and benefits of moderate‐intensity exercise in the management of fetal growth restriction (FGR) are controversial. Objective We sought to evaluate fetal responses to a 30‐min bout of moderate‐intensity exercise in pregnancies complicated by FGR. Study design This prospective study included 28 participants at a single academic institution. Pregnant individuals between 28w0d and 36w6d gestation with a diagnosis of FGR with normal Dopplers were enrolled. FGR was defined as total estimated fetal weight less than 10th percentile for estimated gestational age or abdominal circumference less than 10th percentile. Participants were excluded for body mass index (BMI) > 40, tobacco or substance use, hypertension on medications, or other contraindications to exercise. Participants exercised on a treadmill at a moderate intensity monitored using rate of perceived exertion (Borg scale) for 30 min. Fetal umbilical artery (UA), middle cerebral artery (MCA), aortic Dopplers, and maternal uterine artery Dopplers were sampled immediately before and after exercise. Biophysical profile and non‐stress tests were also performed. Maternal vital signs and rate of perceived exertion were monitored throughout exercise. Cerebro‐placental ratios (CPRs) were calculated after sampling. We hypothesized that there is no significant difference in fetal well‐being or Doppler flow in fetuses with FGR immediately after a 30‐min bout of moderate‐intensity maternal exercise compared to pre‐exercise. Results Biophysical profiles and non‐stress tests were reassuring before and after exercise. The primary outcome of UA Doppler values did not differ from pre‐ to post‐exercise. There was no difference in MCA, aortic Dopplers, or CPR. There was an increase in fetal heart rate ( p < 0.05) post‐exercise, which returned to baseline within several minutes. There was a decrease in uterine artery Dopplers ( p < 0.05) post‐exercise, which was driven by a non‐significant decrease in systolic flow and an increase in diastolic flow. Conclusions In this cohort, there were no acute adverse changes in fetal status after a single bout of moderate‐intensity maternal exercise with fetuses with FGR. These findings add to the limited available data in pregnancies complicated by FGR with normal Dopplers. Additional studies are needed to investigate the fetal and maternal effects of vigorous‐intensity and chronic exercise in this population or in populations with more evidence of placental dysfunction. Clinical trial registration NCT06039319.