This study investigates the relationship between local walkability and physical activity and subsequent health outcomes among pregnant women - for whom walking is the recommended, and by far most common, form of exercise. Using an EPA measure of walkability at the county level (as well as other county-level characteristics) combined with rich individual-level data on pregnant women yields evidence that higher walkability translates into improvements in maternal and infant health outcomes as well as physical activity. Using the 2011 Natality Detail Files with geographic identifiers and controlling for the overall health of women in the community as well as the individual mother's pre-pregnancy BMI, we show that women residing in more walkable counties are less likely to experience preterm birth, low birth weight, gestational diabetes and hypertension. While one potential mechanism is through improved gestational weight gain, the evidence points to more general improvements in health as walkability does not seem to prevent excessive weight gain or macrosomic babies. Evidence that these general improvements derive at least in part from greater physical activity comes from analyses using the 2011 Behavioral Risk Factor Surveillance System, in which higher walkability translates into more physical activity among pregnant women (and also relative to their non-pregnant counterparts). Our study suggests more broadly that pregnant women's physical activity responds to factors that facilitate it and that such activity makes a difference to birth outcomes.
