Until several decades ago, physical activity during pregnancy was a cause for concern because of the perceived associated risk of maternal injury and of physiological changes physical activity induces in blood flow, body temperature, and fetal oxygen delivery that could potentially have both short term and lasting detrimental effects on the fetus.(American College of Sports Medicine 2006) More recently, several observational studies have reported beneficial effects of greater levels of physical activity during pregnancy for the pregnant woman, such as a decreased risk of gestational diabetes (Tobias et al. 2011) and preeclampsia.(Magnus et al. 2008;Rudra et al. 2008) Thus guidelines recommend that pregnant women maintain the same level of moderate physical activity as non-pregnant women.(Artal and O'Toole 2003)

However, current evidence is inconsistent on whether exercise during pregnancy is beneficial, harmful, or neutral for the health of the developing fetus.(Kramer and McDonald 2006) These mixed findings are likely to reflect different methods of exposure and outcome assessment, different timing during the pregnancy for exposure and outcome assessments, differences in pre-pregnancy exercise habits between the study populations, and differences in the studies' abilities to control for potential confounding factors. By far the largest observational study to date, including over 90,000 participants in the Danish National Birth Cohort, found a strong and linear association between increasing levels of physical activity in early pregnancy and miscarriage before 18 weeks gestation.(Madsen et al. 2007) As with other behaviours in pregnancy, RCTs in this area are difficult. However, a Cochrane systematic review of randomized controlled trials to promote aerobic exercise during pregnancy concluded that regular aerobic exercise during pregnancy (mostly swimming, static cycling, floor exercises) appears to improve women's physical fitness, but that current evidence was insufficient to draw firm conclusions about its likely overall risks or benefits for the woman or baby.(Kramer & McDonald 2006) The reviewers concluded that larger, better quality trials are needed before confident recommendations could be made about the benefits and risk of exercise during pregnancy.

The long-term effect of physical activity in pregnancy on offspring future health is even less well studied. Two small prospective studies assessed outcomes in offspring of women who exercised regularly throughout pregnancy compared with offspring of active women who did not exercise at 1 and 5 years of age. In the first study,(Clapp, III et al. 1998) which included 104 mother-offspring pairs, weight, length and abdominal and head circumferences at mean age 1 year were similar in offspring of women who did or did not continue regular physical activity throughout pregnancy. In another study by the same group,(Clapp, III 1996) which included just 40 mother-offspring pairs, at mean age 4 years offspring of women who engaged in vigorous physical activity during pregnancy were lighter and had less subcutaneous fat but were of similar height as offspring of women who voluntarily stopped exercising in pregnancy. They also scored higher for oral language skills and general IQ (assessed by the Wechsler Preschool and Primary Scale Intelligence). Motor, integrative and academic readiness skills were similar between groups. In both studies women were matched for pre and post-natal characteristics known to influence outcomes.(Clapp, III 1996;Clapp, III, Simonian, Lopez, Appleby-Wineberg, & Harcar-Sevcik 1998)

Thus, it is unclear whether variation in levels of physical activity during pregnancy is causally (either beneficially or detrimentally) related to long term health outcomes in offspring. Here we propose to study the association of maternal physical activity during pregnancy with CVD risk factors (including BMI, waist circumference, fat mass, blood pressure, lipids, fasting insulin and glucose) in childhood (age 9 and 15), anti-Mullerian hormone (AMH, a measure of ovarian and testicular function, age 15), cognitive function (age 8) and educational attainment (at age 16 years). We will compare the association of maternal physical activity during pregnancy with the association of paternal physical during pregnancy with the same outcomes. If the association of maternal physical activity with offspring outcomes is greater than the paternal one and remains even when controlling for paternal physical activity, this would suggest a causal, intra utero effect. However, if the associations are of similar magnitude and are abolished with mutual adjustment, this would suggest that familial characteristics such as socioeconomic position or genetic variation are more likely explanations. As a further means of examining whether any associations may be due to intrauterine mechanisms we will examine the extent to which any associations are mediated by offspring levels of physical activity. If the associations are largely or completely explained by offspring activity this would suggest that mechanisms are related to postnatal parental effects on the child's participation in physical activity rather than an effect of physical activity in pregnancy on e.g. risk of preeclampsia and placentation and other pregnancy specific factors that affect fetal development and their later cognitive and cardiovascular health. We will also compare the associations of maternal and paternal physical activity in pregnancy with outcomes measured at different ages, in order to assess whether associations are lasting or perhaps diminish with age.

Our request to include AMH as an outcome here is based on its association with metabolic abnormalities (for example: Park 2003) and we wish to extend a previous application (Prof. Lawlor as the main applicant) to examine smoking, gestational weight gain, blood pressure changes, and diabetes/glycosuria as determinants of offspring AMH.