LEISURE-TIME PHYSICAL ACTIVITY IN PREGNANCY AND BIRTH WEIGHT IN AN AMAZONIAN COHORT STUDY

Objective: To examine the association between LTPA during pregnancy and offspring BW. Methods: Prospective cohort study with 500 pregnant women and their offspring from the MINA-Brazil study, which was conducted in Cruzeiro do Sul, Western Brazilian Amazon. LTPA was assessed in early (median 19.6 gestational weeks) and late (median 27.8 weeks) pregnancy by a standardised interview and categorised according to the recommended international 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). Results: At least 150 min/week of LTPA during late pregnancy 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 early or in late pregnancy (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. Conclusions: LTPA in late, but not in early, pregnancy was inversely associated with offspring BW without increasing the frequency of SGA, an effect that was partly mediated by excessive GWG. Thus, the recommended levels of LTPA should be encouraged during prenatal care, especially for women with excessive weight gain.