Long Commute to Work during Pregnancy and Infant Health at Birth

In the United States, according to the most recent census data, approximately 2.2 million workers travel at least 50 miles each way between their homes and workplaces, and about 1.7 million workers spend 90 minutes or more commuting in each direction. These long commutes can be physically and mentally demanding, particularly for pregnant women. In this regard, we conduct the first empirical study to examine the health impact of long commute to work during pregnancy on fetuses and infants at birth, using unique data that contain information on not only a woman's home address but also her employer's address during her pregnancy. Our study is also the first to examine the health impact of the chronic strain induced by long commute on fetuses and infants at birth, adding new evidence to the literature.

We find that among long-distance commuters, increasing the maternal travel distance during pregnancy by 10 miles is associated with increases in low birth weight and intrauterine growth restriction by 1.0 and 0.6 percentage points, or 25 and 46 percent compared with their means, respectively. In addition, we provide evidence on two possible mechanisms underlying the adverse health outcomes associated with long commute: elevated stress levels of pregnant women who are long-distance commuters, and under-utilization of prenatal care.

We examine the presence of long commute induced maternal stress during pregnancy by showing that the likelihood of using c-sections increases among male babies, but not among female babies, born to women who travel long distance to work during pregnancy. Such an increase is consistent with the finding in the medical literature that male fetuses are more sensitive to stressors in utero than female fetuses, resulting in higher likelihood of delivery complications that require c-sections. With regard to prenatal care, we find that among long-distance commuters an increase of 10 miles in maternal travel distance during pregnancy could reduce the number of prenatal visits by 2.53 percent, decrease the probability of the mother’s completing her first prenatal visit within the first trimester by 2.3 percentage points, and increase the probability of the mother's completing her first prenatal visit within the third trimester or having no prenatal visit at all by 1.4 percentage points, all indicating an under-utilization of prenatal care.

In addition, our study is the first to calculate the travel distance according to existing public roads instead of using the commonly computed geodetic distance, which represents the length of the shortest curve between two points on earth. Using geodetic distance can incur a greater attenuation bias, potentially leading to a claim of no adverse effect of long commute when the adverse effect could be detected by a less noisily measured commuting distance.

Our study has important implications for public policy proposals that consider expanding maternity leave to cover the prenatal period, particularly in the context of the United States. Having the needed time off during the prenatal period can be crucial for pregnant women who are long commuters to alleviate stress and adequately utilize prenatal care.