The benefits of prenatal care: evidence from the PAT bus strike

Using data from the 1990-1994 Natality Detail files, we examine the impact of prenatal visits on birth outcomes using the 1992 Port Authority Transit strike in Allegheny County, Pennsylvania as an exogenous source of variation in access to prenatal care. Our first-stage estimates demonstrate that black-inner city women pregnant at the time of the strike experienced a sharp decline in prenatal care visits. Using the bus strike as an instrument for prenatal care in birth outcome equations, we find that two-stage least-squares (2SLS) estimates of the impact of prenatal care on birth weight, gestation and maternal weight gain are similar to single-equation estimates. The 2SLS estimates are however imprecisely estimated. There is consistent and precise evidence that prenatal care visits reduced maternal smoking. Because the strike impacted women at different points in their pregnancy, we can isolate the impact of missing prenatal visits early or late in a pregnancy. We find suggestive evidence that visits lost early in the pregnancy negatively impact birth outcomes but there is little evidence of a cost to missing a visit late in the pregnancy. Our results do demonstrate the importance of public transportation in health care delivery for some groups.