Leisure time physical exercise during pregnancy and the risk of miscarriage: a study within the Danish National Birth Cohort

Maternal sleep deprivation, sedentary lifestyle and cooking smoke: Risk factors for miscarriage: A case control study

“…Maden et al 22 had examined the association between leisure time physical exercise and risk of miscarriage and found that women who exercised more than 7 h/week had an increased risk up to 18 weeks of pregnancy. In contrast to these results, swimming for 75–269 min/week was shown to decrease the risk of miscarriage, defined here as period of gestation up to 22 weeks 22 . One study had reported that a single bout of maximum symptom‐limited exercise does not have immediate adverse fetal or maternal cardiovascular effects 23 .…”

Information bias in epidemiological studies with a special focus on obstetrics and gynecology

“…These women retrospectively reported on physical exercise (retrospectively in relation to the outcome). Although the analyses of all women showed a consistently increasing risk of miscarriage with increasing time spent on physical exercise (compared with no exercise), no association was seen between physical exercise and miscarriage after exclusion of the women providing exposure information retrospectively . As random error is a highly unlikely explanation for such a systematic change in results, the most plausible explanation is differential misclassification, as those women having already experienced a miscarriage overreported physical activity level relative to those who had not (recall bias).…”

“…By early inclusion, such as has been the case in some of the largest birth cohorts worldwide , even suspicion of these conditions in early pregnancy is unlikely to influence the risk of misclassification. However, even if early inclusion is attempted, studies on early miscarriage will often be affected by differential rather than non‐differential misclassification .…”

“…In a cohort study of the association between physical exercise and risk of miscarriage , which was carried out in the Danish National Birth Cohort, the vast majority of women provided information of the exposure prior to the miscarriage (or birth in case of no miscarriage). However, because of the recruitment procedure, some women miscarried in the time interval between agreeing to participate and the actual baseline interview.…”

Moderate impact of full‐term pregnancy on estimated peak oxygen uptake, physical activity and perceived health

“…Moderate prenatal exercise is useful in improving physiological reserves and aerobic fitness without affecting fetal growth (6–11). Thus, maintaining light to moderate physical activity is recommended during an uncomplicated pregnancy (12), whereas higher levels of physical activity may be questioned (13).…”