Abstract
Compelling evidence supports the current international recommendation of at least 150 min/week of leisure-time physical activity (LTPA) during pregnancy. However, the potential relationship between LTPA and birth weight (BW) remains unclear in low- and middle-income countries. The purpose of this study was to examine the association between LTPA during pregnancy and offspring BW in an Amazonian population. Prospective cohort study was carried-out with 500 pregnant women and their offspring followed-up in the MINA-Brazil study, which was conducted in Cruzeiro do Sul, Western Brazilian Amazon. LTPA was assessed in the second (mean 19.6, SD 2.4 weeks) and third (mean 27.8, SD 1.6 weeks) gestational trimesters by a standardised interview and categorised according to the recommended cut-off of at least 150 min/week. We calculated offspring BW z-scores by sex and gestational age. We then explored the effect of LTPA during pregnancy on offspring BW, the association between LTPA and small-for-gestational-age (SGA) or large-for-gestational-age (LGA) births, and the mediating role of excessive and insufficient gestational weight gain (GWG). At least 150 min/week of LTPA during the third gestational trimester was associated with an offspring BW decrease of -0.35 z-score (95% CI: -0.65, -0.05) or -147.9 grams (95% CI: -260.9, -14.8), without increasing the frequency of SGA foetuses either in the second or third gestational trimester (p > 0.05). Excessive GWG mediated the effect of LTPA on the offspring BW (indirect effect = -0.05 z-score [95% CI: -0.10, -0.00] or -34.7 grams (95% CI: -66.1, -3.3]). This mediation effect was not observed for insufficient GWG. LTPA in the third, but not in the second, trimester of pregnancy was inversely associated with offspring BW without increasing the frequency of SGA, an effect that was partly mediated by excessive GWG.
Highlights
Substantial scientific evidence supports the current international recommendation of at least 150 min/week of leisure-time physical activity (LTPA) during pregnancy [1, 2]
No evidence of mediation through insufficient gestational weight gain (GWG) was observed, considering a natural indirect effect (NIE) of -6.4 grams (p = 0.659). This prospective cohort study among Amazonian women showed that LTPA in the third trimester of pregnancy, but not in the second trimester of pregnancy, was inversely associated with offspring birth weight (BW)
Achieving at least 150 min/week of LTPA in the third trimester of pregnancy was associated with decreased offspring BW without increasing the frequency of smallfor-gestational age foetuses
Summary
Substantial scientific evidence supports the current international recommendation of at least 150 min/week of leisure-time physical activity (LTPA) during pregnancy [1, 2]. Cohort studies showed that almost 50% of women performed regular exercise before pregnancy, but this figure declined at the second to third gestational trimester [7– 9]. The same meta-analysis evaluated six cohort studies (n = 62,127 women) and showed LTPA had a small decreased effect on mean BW, with no heterogeneity [8, 11]. A recent meta-analysis comprising 72,694 participants (mainly white women) from a consortium of eight studies (seven European and one American) showed that every additional hour per week of moderate to vigorous physical activity in late pregnancy decreased BW by 6.4 grams with decreased risks of macrosomia and LGA by 4% and 3%, respectively; no association was found between LTPA in early pregnancy and BW [16]
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