The potential relationship between daily physical activity and pregnancy outcome remains unclear because of the wide variation in study designs and physical activity assessment measures. We sought to prospectively quantify the potential effects of the various domains of physical activity on selected birth outcomes in a large unselected population. The sample consisted of 11,759 singleton pregnancies from the Avon longitudinal study of parents and children, United Kingdom. Information on daily physical activity was collected by postal questionnaire for self-report measures. Main outcome measures were birth weight, gestational age at delivery, preterm birth and survival. After controlling for confounders, a sedentary lifestyle and paid work during the second trimester of pregnancy were found to be associated with a lower birth weight, while 'bending and stooping' and 'working night shifts' were associated with a higher birth weight. There was no association between physical exertion and duration of gestation or survival. Repetitive boring tasks during the first trimester was weakly associated with an increased risk of preterm birth (<37 weeks) (adjusted odds ratio [OR] = 1.25, 95% CI 1.04-1.50). 'Bending and stooping' during the third trimester was associated with a reduced risk of preterm birth (adjusted OR = 0.73, 95% CI 0.63-0.84). Demanding physical activities do not have a harmful effect on the selected birth outcomes while a sedentary lifestyle is associated with a lower birth weight. In the absence of either medical or obstetric complications, pregnant women may safely continue their normal daily physical activities should they wish to do so.

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Keywords Birth weight, Gestational duration, Motor activity, Perinatal mortality, Premature birth, United Kingdom, article, birth weight, body posture, cohort analysis, controlled study, delivery, employment status, female, gestational age, health survey, human, longitudinal study, low birth weight, night work, outcome assessment, perinatal mortality, physical activity, population research, pregnancy outcome, pregnant woman, prematurity, risk assessment, second trimester pregnancy, self report, survival rate, third trimester pregnancy
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Journal European Journal of Epidemiology
Both, M.I, Overvest, M.A, Wildhagen, M.F, Golding, J, & Wildschut, H.I.J. (2010). The association of daily physical activity and birth outcome: A population-based cohort study. European Journal of Epidemiology, 25(6), 421–429. doi:10.1007/s10654-010-9458-0