Bed rest during pregnancy: a favourable condition for fetal weight gain?

Nearly one woman in five will have to reduce her activities or be at complete rest at some point during her pregnancy. Yet studies examining the effects of bed rest are rare, particularly when it comes to fetuses with intrauterine growth retardation (IUGR).When IUGR is observed, the current approach advocates increased monitoring with a series of biometric tests to assess fetal well-being and schedule the birth at the appropriate time. Short-term bed rest appears to be beneficial for babies with low gestational weight, according to a new U.S. observational study. It suggests that two weeks’ complete rest for the mother would be sufficient for the fetus to cross the 10th percentile mark and maintain it to term. The researchers rested 265 mothers whose fetuses showed IUGR during a second-trimester ultrasound. For the next two weeks, they were confined to bed in the left lateral position, avoiding the supine position. The women got up every hour to walk, stretch or attend to personal needs for five to 10 minutes.Read: Dr. Ginevra Mills: From doubt to deliveryAn ultrasound scan at the end of the two weeks revealed that 75% of the fetuses were above the 10th percentile. Specifically, the median percentile had risen from 6.8 to 18. These data are superior to those from two control groups whose mothers were not prescribed rest despite IUGR. For each of these groups, the 10th percentile was crossed in 19% and 12% of cases respectively.Rest had benefits on other biometric parameters. The median percentile for abdominal circumference jumped by 12 points, from 5 to 17. Femoral length and head circumference also increased, albeit more modestly.It is already recognized that lying in the left lateral position improves maternal cardiac output and uterine blood flow, which would explain these improvements.Effects for the rest of the pregnancyIn two-thirds of cases, the growth rate continued to accelerate in the weeks following bed rest, before stabilizing at the last examination, around the 38th week of amenorrhea. The beneficial effects of maternal rest would therefore be long-lasting for a certain proportion of newborns. However, for almost 20% of them, the results were not sustained. An ultrasound scan at the end of pregnancy again showed fetal weight below the 10th percentile.“If a significant increase in fetal weight can be achieved with fewer hours of rest, this would be preferable for the mother. Randomized studies could investigate the effects of variable rest duration on fetal response,” propose the authors of the study published in the American Journal of Obstetrics & Gynecology.Among the study’s limitations is the absence of neonatal follow-up. Thus, it is not known whether rest had any impact on postnatal parameters or whether it led to a reduction in the risks associated with poor intrauterine growth, notably the risk of cardiovascular disease. In 2022, a prospective cohort study had indeed found that IUGR could affect cardiac function from the very first months of life.

Bed rest during pregnancy: a favourable condition for fetal weight gain?

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