Associations between maternal physical activity and fitness during pregnancy and infant birthweight

Influence of Physical Activity during Pregnancy on Birth Weight: Systematic Review and Meta-Analysis of Randomized Controlled Trials

Birth weight is a marker that is often referred to determine newborn health, potential growth trajectories and risk of future disease. Accordingly, interventions to promote appropriate and healthy birth weight have been extensively studied and implemented in pregnancy. In particular, physical activity in pregnancy is recommended to promote appropriate fetal development and newborn birth weight. This systematic review and meta-analyses aimed to summarize the effect of physical activity during pregnancy specifically from randomized controlled trials on the following outcomes: birth weight, macrosomia, low birth weight, being large for the gestational age, and being small for the gestational age (Registration No.: CRD42022370729). 63 studies (16,524 pregnant women) were included. There was a significant negative relationship between physical activity during pregnancy and macrosomia (z = 2.16; p = 0.03; RR = 0.79, 95% CI = 0.63, 0.98, I2 = 29%, Pheterogeneity = 0.09). No other significant relationships were found. Promoting physical activity during pregnancy may be an opportune time to reduce the risk of future chronic disease, such as obesity, through the prevention of macrosomia and the promotion of appropriate birth weights.

Effects of Maternal Exercise During Pregnancy on Perinatal Growth and Childhood Obesity Outcomes: A Meta-analysis and Meta-regression

BACKGROUND

Perinatal growth abnormalities program susceptibility to childhood obesity, which is further exaggerated by maternal overweight and obesity (MO) during pregnancy. Exercise is highly accessible, but reports about the benefits of maternal exercise on fetal growth and childhood obesity outcomes are inconsistent, reducing the incentives for pregnant women to participate in exercise to improve children's perinatal growth.

OBJECTIVE

This systematic review and meta-analysis aims to establish evidence-based efficacy of exercise in mothers with normal weight (MNW) and MO during pregnancy in reducing the risks of perinatal growth abnormalities and childhood obesity. In addition, the impacts of exercise volume are also assessed.

METHODS

The PubMed, ScienceDirect, Web of Science, and Cochrane Library databases were searched from inception to February 15, 2020. We included randomized controlled trials with exercise-only intervention or exercise with other confounders in pregnant MNW (body mass index, BMI 18.5-24.9 kg/m²) and MO (BMI ≥ 25 kg/m²), which were further subgrouped in the meta-analysis. Primary outcomes included birth weight, preterm birth, small for gestational age (SGA), large for gestational age (LGA), infant and childhood weight, and childhood obesity. A linear meta-regression analysis was also used to explore the effects of exercise volume on outcomes.

RESULTS

99 studies were included in the meta-analysis (n = 596,876), and individual study quality ranged from fair to good according to the Newcastle-Ottawa scale assessment. Exercise only interventions in MNW reduced preterm birth by 15% (26 studies, n = 76,132; odds ratio [OR] 0.85; 95% CI 0.72, 1.01; I² = 83.3%), SGA by 17% (33 studies, n = 92,351; OR 0.83; 95% CI 0.71, 0.98; I² = 74.5%) and LGA by 17% (29 studies, n = 84,310; OR 0.83; 95% CI 0.74, 0.95; I² = 60.4%). Exercise only interventions in MO reduced preterm birth by 33% (2 studies, n = 3,050; OR 0.67; 95% CI 0.70, 0.96; I² = 0%), SGA by 27% (8 studies, n = 3,909; OR 0.73; 95% CI 0.50, 1.05; I² = 40.4%) and LGA by 55% (9 studies, n = 81,581; OR 0.45; 95% CI 0.18, 1.11; I² = 98.3%). Exercise only interventions in MNW reduced childhood obesity by 53% (3 studies, n = 6,920; OR 0.47; 95% CI 0.36, 0.63; I² = 77.0%). However, no significant effect was observed in outcomes from exercise confounders in either MNW or MO. In the meta-regression, the volume of exercise-only intervention in MNW was negatively associated with birth weight, greatly driven by volumes more than 810 metabolic equivalents (MET)-min per week. Other outcomes were not associated with exercise volume.

CONCLUSIONS

This systematic review and meta-analysis suggests that exercise during pregnancy in both MNW and MO safely and effectively reduce the risks of preterm birth, SGA, and LGA. Furthermore, MNW exercise also reduces the risk of childhood obesity. Overall, regardless of prepregnancy BMI, maternal exercise during pregnancy provides an excellent opportunity to mitigate the high prevalence of adverse birth outcomes and childhood obesity.