Article Text
Abstract
Aim To evaluate the association between maternal physical activity and infant’s birth weight or risk of inappropriate weight for gestational age (GA), and whether this association differs by infant’s sex, maternal body mass index (BMI) or pregnancy complications in a prospective cohort study.
Methods 1913 pregnant women from the 3D Birth Cohort (Québec, Canada) completed the Pregnancy Physical Activity Questionnaire at each trimester. Energy expenditure (metabolic equivalent of task (MET)*hours/week) for total activity, sports and exercise and vigorous intensity activities was calculated. The associations with birth weight and risk of inappropriate weight for GA were evaluated by regression modelling. Interactions were tested with infant’s sex, maternal prepregnancy BMI, gestational diabetes, hypertensive disorders and prematurity.
Results Each 1 MET/hours/week increase in sports and exercise in the first trimester was associated with a 2.5 g reduction in infant’s birth weight (95% CI −4.8 to −0.3) but was not associated with the risk of small weight for GA. In contrast, although not significant, a 17% reduction in the risk of large weight for GA was observed with increasing sports and exercise. Furthermore, in women with subsequent pre-eclampsia (but not normotensive or hypertensive women), each 1 MET/hours/week increment spent in any vigorous exercise in the first trimester reduced the infant’s birth weight by 19.8 g (95% CI −35.2 to −4.3).
Conclusions Pregnant women with higher sports and exercise levels in the first trimester delivered infants with a lower birth weight. The risk of reducing infant’s birth weight with vigorous exercise in women who develop pre-eclampsia later in pregnancy requires evaluation.
- exercise
- growth
- physical activity
- pregnancy
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Footnotes
Acknowledgements This project was conducted as part of the research programme of the Integrated Research Network in Perinatology of Quebec and Eastern Ontario (IRNPQEO). The authors thank all the recruiting centres involved in this study, and Dr Alexandre Bureau, professor at the Department of Social and Preventive Medicine, Université Laval, for statistical support and revision of the statistical methods and interpretation.
Contributors WDF is the principal investigator for the 3D Birth Cohort and IM was in charge of the physical activity assessment. WDF, IM, EB and FA supervised data collection. IM, MB and JC developed the study hypotheses, and planned and performed data analyses. MB and IM wrote the original draft, and all the authors (BCG, WDF, EB, FA, JC) commented on the draft, contributed to the interpretation of the findings and had final approval of the submitted version.
Funding This work was supported by the Canadian Institutes of Health Research [CRI 88413]. MB is supported by a doctoral scholarship from the Canadian Institutes of Health Research. The funder had no role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.
Competing interests None declared.
Ethics approval The Research Ethics Board of the Centre de recherche du Centre hospitalier universitaire Sainte-Justine approved the initial protocol (reference number CHU-HSJ-2009-010) on 19 April 2010.
Provenance and peer review Not commissioned; externally peer reviewed.
Correction notice This paper has been amended since it was published Online First. Owing to a scripting error, some of the publisher names in the references were replaced with 'BMJ Publishing Group'. This only affected the full text version, not the PDF. We have since corrected these errors and the correct publishers have been inserted into the references.