Does Greater Exposure to WIC Affect Maternal Behavior and Improve Infant Health? Evidence from the Pregnancy Nutrition Surveillance System
- Presenter:
Chair: Michael Grossman; Discussant: Robert Kaestner Tue June 6, 2006 15:30-17:00 Room 332
Benefits of the Supplemental Program for Women, Infants and Children (WIC) that may impact maternal behavior and birth outcomes include nutritional supplementation, nutritional counseling, health care referrals, and breastfeeding promotion. We propose to test whether earlier and sustained exposure to program benefits results in less maternal smoking, greater weight gain, more breastfeeding and therefore healthier pregnancies and infants. However, instead of comparing WIC to non-WIC participants, we compare women who enroll in WIC in the first trimester of pregnancy to women who either enroll later in pregnancy or in the postpartum period. In other words, everyone in our sample will have “selected” into WIC between conception and the first postpartum visit. We appreciate that many of the selection issues present in comparisons of WIC and non-WIC women may also be present in an analysis of WIC participants only. Therefore, we stratify the analysis by the parity and the timing of the first prenatal care visit in order to lessen selection within WIC participants. Specifically, we focus on women with no previous live births, all of whom begin prenatal care in the first trimester. Some are certified for WIC in the first trimester and some not until after birth. The key to our empirical strategy is data with a large number of WIC participants, detailed information on the timing of their WIC certification, and a rich set of maternal behaviors. The Pregnancy Nutritional Surveillance System (PNSS) in North Carolina and New Jersey meets these requirements.(http://www.cdc.gov/pednss/). The systems in North Carolina and New Jersey collect information on approximately 40,000 women and their infants each year. We will analyze data from both states from 1995-2003 and thus have upwards of 600,000 observations. The PNSS collects data on body mass index, hematocrit level, smoking cessation, and breastfeeding. The greater detail makes PNSS superior to birth certificates along numerous dimensions. However, like birth certificates the samples are large and thus we are able to stratify the analysis not only by the parity and the timing of prenatal care, but race and ethnicity as well. Preliminary results indicate that greater exposure to WIC is uncorrelated with smoking session and weight gain during pregnancy. Consistent with these findings, we find no difference in birth outcomes among women who enrolled in WIC in the first trimester, second or third trimester. These results are in agreement with recent work that has challenged a causal association between prenatal WIC participation and improved birth outcomes.
