Maternal periconceptional physical activity, sedentary behavior, and offspring growth
BACKGROUND
Current guidelines recommend regular moderate/vigorous physical activity before and during pregnancy to reduce pregnancy complications. However, the recommendations do not include light physical activity or address fetal and postnatal growth. While reductions in sedentary behavior, in addition to regular moderate/vigorous physical activity, have been recommended for the general population, little is known about the effect of maternal sedentary behavior before and during pregnancy on offspring in utero or postnatal growth. In addition, consequences of long-term patterns of preconception physical activity during young adulthood, offspring sex-specific differences in associations, as well as potential mechanisms of observed associations have not been adequately investigated.
OBJECTIVES
The specific aims of this dissertation project were to investigate associations of 1) maternal pre-pregnancy and early pregnancy light physical activity and sedentary behavior with measures of offspring birth size, 2) maternal early pregnancy moderate/vigorous physical activity and sedentary behavior with offspring growth at 12 months of age, 3) trajectories of maternal preconception moderate/vigorous physical activity and sedentary time during adolescence and young adulthood with offspring birthweight, and 4) maternal pre-pregnancy and early pregnancy moderate/vigorous physical activity and epigenetic regulation in maternal peripheral blood.
METHODS
Aim 1 was addressed using data from participants (N=3,687) of the Omega study, a pregnancy cohort study based in Seattle, WA. Aim 2 was addressed using data from participants (N=40,638) of the Danish National Birth Cohort (DNBC). Aim 3 was addressed using data from participants (N=1,408) of the National Longitudinal Study of Adolescent to Adult Health (Add Health). Aim 4 was addressed using data and specimens collected from a subset (N=92) of Omega study participants. I used self-reported leisure time physical activity and sedentary behavior before and during pregnancy, information on offspring birth size and offspring weight at 12 months from medical records (Omega study) or maternal report (DNBC and Add Health), and epigenetic biomarkers (DNA methylation and microRNA expression) in peripheral blood (Aim 4), as well as information on relevant covariates in regression (linear and logistic) models and group-based trajectory analyses (Aim 3) to examine associations. Offspring sex-specific associations were evaluated using interaction terms and stratified analyses.
RESULTS
Leisure time walking in the year before pregnancy and in early pregnancy were positively associated (0.8 kg/m3 comparing the highest tertile to no walking (95% CI: 0.2, 1.4 and 0.2, 1.3, respectively)) with greater offspring ponderal index at birth (Aim 1). Moderate/vigorous leisure time physical activity in early pregnancy was inversely associated (0.01 kg per hour per week (95% CI: -0.02, -0.001)) with offspring weight at 12 months old among males, but not females (Aim 2). Early pregnancy leisure time sedentary behavior was also inversely associated (0.09 kg comparing 5+ hours per day to 0-1 hours per day (95% CI: -0.17, -0.003)) with offspring weight at 12 months old (Aim 2). I identified sex-specific associations of a pattern of preconception moderate/vigorous physical activity characterized by high physical activity at age 15 years followed by decreasing physical activity by age 22 years compared to a pattern of low then decreasing physical activity from ages 15-22 years with 90g (95% CI: -4, 184) greater birthweight and 1.7 (95% CI: 0.9, 3.1) times greater odds of large-for-gestational age among female offspring, but not male offspring (Aim 3). I did not observe associations of pre-pregnancy or early pregnancy yoga practice with offspring birth size (Aim 1) or associations of maternal pre-pregnancy or early pregnancy sedentary behavior with offspring birth size (Aim 1 and 3). Each additional hour per week of pre-pregnancy and early pregnancy moderate/vigorous physical activity were associated with peripheral blood DNA methylation in C1orf212 and circulating miR-146b expression (Aim 4).
CONCLUSIONS
Our results support associations of maternal physical activity with offspring birth size, postnatal growth, and maternal epigenetic regulation. Our results also support associations of maternal sedentary behavior with offspring postnatal growth. Several of these associations were sex-specific. Future research in this area, conducted in diverse populations and using objective measurement to capture accurate measures of time spent in these behaviors across multiple domains, will facilitate adoption of effective interventions to promote physical activity among reproductive age and pregnant women and improve maternal and fetal health outcomes.