“…Consistent with the notion that birth outcomes are affected both by biomedical and by psychosocial factors, medical risk and parity (whether or not a woman has given birth previously) are two of the most important biomedical predictors of birth outcome (Binsacca et al, 1987;Buescher et al, 1988;Cramer, 1987;Dott and Fort, 1975;Institute of Medicine, 1985;Shiono et al, 1986) and should therefore be controlled when examining the impact of prenatal stress on birth outcome. Some studies have used samples homogeneous in medical risk and parity to control for the effects of these characteristics (e.g., Bradley, 1983;Lederman et al, 1979;Levi et al, 1989;Picone et al, 1982). However, the results of such studies may not be generalizable to populations of different risk level or parity.…”