Maternal Physical Activity During Pregnancy

Abstract

PURPOSE: Maternal physical activity during pregnancy influences infant’s birth weight and body composition, but its association with bone health has been poorly evaluated. This study aims at documenting in a longitudinal study the effect of objectively measured physical activity during pregnancy on infant’s bone mineral content (BMC) and density (BMD). METHODS: 7-day accelerometry recordings (Actigraph GT3X+) were performed in low-risk pregnant women at 17 and 36 weeks of gestation. BMC and BMD were evaluated by DXA in mothers and infants within 2 weeks after birth. Sociodemographics, maternal lifestyle habits, pre-pregnancy physical activity, medical history and pregnancy outcomes were collected through interview and charts’ review. Mean counts per minute (CPM) and daily time spent at moderate and vigorous physical activity (MVPA) were calculated for each period from accelerometry data. The association between physical activity data and infant’s BMC and BMD was evaluated through multiple regression models, adjusting for infant sex and length, parity, maternal pre-pregnancy BMI, gestational weight gain, multivitamin use, gestational age at delivery, infant’s age at DXA, maternal BMD and pre-pregnancy physical activity. RESULTS: : For this preliminary analysis, DXA assessment and accelerometry data for at least one visit were available for 108 pregnant women (age=29.7 ± 3.7 y; pre-pregnancy BMI=23.6 ± 4.7 kg/m2; 59.3% nulliparous) and their baby (birth weight=3451 ± 424 g; gestational age=39.7 ± 1.2 weeks; 45.4% boys). Daily time spent at MVPA at 17 weeks was negatively associated with infant’s BMC and BMD (β= -0.45 g and -0.0009 g/cm3 per 10 min of MVPA, p=0.033 and 0.026), after adjustment for confounders. Similarly, mean CPM at 17 weeks was significantly associated with infant’s BMC and BMD (β= -1.92 g and -0.004 g/cm3 per 100 CPM, p=0.010 and p=0.004). Mean CPM at 36 weeks was also associated with child’s BMC (β= -0.004 g/cm3 per 100 CPM, p=0.024). CONCLUSIONS: Higher levels of maternal physical activity measured by accelerometry during pregnancy were associated with a decrease in infant’s BMC and BMD. The impact of maternal nutrition on this association remains to be investigated. Supported by the Fondation des Étoiles, Canadian Institutes of Health Research and Fonds de Recherche du Québec-Santé.