Effects of psychosocial risk factors and prenatal interventions on birth weight: evidence from New Jersey's HealthStart program.

CONTEXT Many states developed and implemented multifaceted Medicaid prenatal care programs in the late 1980s in response to expansions in Medicaid eligibility. Although these new programs were based on the presumed relationships between psychosocial risk factors, early prenatal care, prenatal interventions and birth outcomes, research has not verified all of these linkages. METHODS Data were collected on 90,117 women who took part in New Jersey's comprehensive prenatal care program, HealthStart, between 1988 and 1996. The impact of psychosocial risk factors and prenatal interventions on mean birth weight and the odds of low birth weight (less than 2,500 g) was assessed using ordinary least-squares regression and logistic regression, respectively. RESULTS After controls were introduced for social and demographic, psychosocial and behavioral factors, as well as the woman's county of residence and the year of her baby's birth, smoking, drinking and using hard drugs (but not marijuana) during pregnancy were independently associated with reductions in mean birth weight (of 123g, 29g and 137g, respectively) and with increases in the odds of low birth weight (odds ratios, 1.4, 1.2 and 1.7, respectively). However, according to the fully adjusted model, which also controlled for medical risk factors and prenatal services, the interventions designed to reduce those behaviors had no favorable effects on birth weight. In contrast, the receipt of services in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) was associated with an increase in mean birth weight of 22g (and of 48g among inadequately nourished women only), and with a reduction in the risk of low birth weight (odds ratio, 0.87). CONCLUSION Referrals to WIC services should be a key feature of prenatal care programs for poor women.