Longitudinal Changes in Physical Activity during Pregnancy: National Institute of Child Health and Human Development Fetal Growth Studies.

Introduction: Exercise in pregnancy is associated with many perinatal benefits, but patterns of home, work, and commuting activity are not well described. We investigated longitudinal activity in singleton and twin pregnancy by activity domain and maternal characteristics.

Methods: In the National Institute of Child Health and Human Development Fetal Growth Studies cohorts, 2778 women with singleton and 169 women with twin gestations reported activity using the Pregnancy Physical Activity Questionnaire at up to six or seven study visits, respectively. Metabolic equivalent of task-hours per week (MET-h·wk -1 ) was calculated from reported activity. Baseline measurements (obtained between 10 and 13 wk) reflected past year activity. Linear mixed models estimated MET-h·wk -1 by domain (household/childcare, occupational, inactive, transportation, sports/exercise), self-reported race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, Asian/Pacific Islander), prepregnancy body mass index (<25, 25 to < 30, ≥30 kg·m -2 ), parity (0, ≥1), baseline activity (quartiles), and plurality (singleton, twin).

Results: Household/caregiving activity made up the largest fraction of reported MET-h·wk -1 at baseline (42%), followed by occupational activity (28%). Median summed activity declined 47%, from 297 to 157 MET-h·wk -1 , between 10 and 40 wk, largely driven by changes in household/caregiving (44% decline), and occupational activity (63% decline). Sports/exercise activity declined 55% but constituted only 5% of reported MET-h·wk -1 at baseline. At baseline, non-Hispanic Black women reported significantly higher activity than non-Hispanic White or Hispanic women, but differences did not persist across pregnancy. Across gestation nulliparous women reported significantly lower activity than parous women. Women with singleton gestations reported significantly more activity than women with twins from weeks 26 to 38. Baseline activity level was strongly associated with later activity levels.

Conclusions: Measuring domains of activity beyond exercise, and collecting longitudinal measurements, is necessary to fully describe activity in diverse populations of pregnant women.