The National WIC Evaluation: evaluation of the Special Supplemental Food Program for Women, Infants, and Children. I. Background and introduction.

The Special Supplemental Food Program for Women, Infants, and Children (WIC) aims to improve the nutrition and health of low-income, nutritionally at-risk pregnant women and preschool children with supplemental food, nutrition education, and coordination of health care. Started in 1972, it recently served greater than 3.4 million persons monthly and at a cost of $1.66 billion annually. The National WIC Evaluation (NWE) consisted of four studies: The historical study estimated changes in birth outcome attributable to WIC from 1972 to 1980 in 19 states and the District of Columbia from WIC program data and vital statistics. The longitudinal study of pregnant women compared dietary intake, weight gain, anthropometry, duration of gestation, birth weight, and infant length and head circumference between a representative national sample of WIC participants and economically comparable women. The cross-sectional study of preschool children related WIC to dietary intake, anthropometry, and psychological development. The food expenditures study estimated the impact of WIC on family grocery and other food expenditures.

The National WIC Evaluation: evaluation of the Special Supplemental Food Program for Women, Infants, and Children. III. Historical study of pregnancy outcomes.

We related perinatal outcome and quality of prenatal care between 1972 and 1980 to WIC benefits to pregnant women among 11,154,673 births in 1392 counties in 19 states and the District of Columbia, adjusted for time change and between-county variability. WIC was associated with increased first trimester prenatal care (4.1%, p less than 0.001), decreased inadequate prenatal care (-5.0%, p less than 0.001), longer duration of gestation (0.20 d, p less than 0.05), decreased preterm delivery (-0.92%, p less than 0.05) and increased birth weight (23 g, p less than 0.01). After autocorrelation was accounted for, significance levels for birth weight and frequency of preterm delivery were 0.05 less than p less than 0.10. Including counties with incomplete time series data, the estimated effect on birth weight was 23.9 g (p = 0.004) and on decreased fetal mortality was -2.3/1000 (p = 0.04). Among those with less than 12 y schooling, whites had a 1.8% reduction in preterm birth (p less than 0.05) and blacks a 2.0% reduction (p less than 0.05). The estimated effect on birth weight for less-educated whites was 46.6 g (p less than 0.001). The predominant effects of WIC were on improved physiologic status of the mother and fetus.

The National WIC Evaluation: evaluation of the Special Supplemental Food Program for Women, Infants, and Children. IV. Study methodology and sample characteristics in the longitudinal study of pregnant women, the study of children, and the food expenditures study.

The longitudinal study of pregnant women enrolled a national probability sample of 5,205 women first certified for WIC and 1,358 comparable low-income pregnant women in 174 WIC clinics located in 58 areas in the contiguous 48 states and in 55 prenatal clinics without WIC programs in counties with low program coverage. The women completed 24-h dietary recalls, histories of food expenditures, health care utilization, health and sociodemographic status, and anthropometric assessment. At late-pregnancy follow-up 3,967 WIC and 1043 control women were interviewed and 853 WIC and 762 control women completed 1-wk food expenditure diaries. Birth outcome was abstracted (from hospital records) for 3,863 WIC and 1058 control women. Anthropometry, dietary intake, health, and use of health services were related to WIC among 2,619 random low-income preschoolers. Psychological development was assessed in 526 children aged 4 and 5 y. Control women had higher income, education, and employment status; therefore, WIC program benefits probably were underestimated.

The National WIC Evaluation: evaluation of the Special Supplemental Food Program for Women, Infants, and Children. V. Longitudinal study of pregnant women.

The major associations with the Special Supplemental Food Program for Women, Infants, and Children (WIC) in pregnancy were increased intake of protein, iron, calcium, and vitamin C (four of five targeted nutrients) and of energy, magnesium, phosphorus, thiamin, riboflavin, niacin, vitamin B-6, and vitamin B-12; reversal of low weight gain in early pregnancy; smaller fat stores in late pregnancy; reduced frequency of premature rupture of the uterine membranes; larger infant head circumference with no effect on birth weight and length; increased birth weight and head circumference with better program quality; and lower fetal mortality of appreciable but not significant magnitude. Incremental energy intake was comparable to that in most small-scale supplementation trials. There was no evidence of effects on frequency of prenatal care, use of alcohol or tobacco, the intention to breast-feed, or the rate of breast-feeding. Maternal alcohol intake was associated with depressed infant head circumference, over and above effects on birth weight and length.

The National WIC Evaluation: evaluation of the Special Supplemental Food Program for Women, Infants, and Children. VI. Study of infants and children.

The major associations with the Special Supplemental Food Program for Women, Infants, and Children (WIC) in preschool children were better dietary intake associated with current WIC participation, especially for Fe, vitamin A, and vitamin C, but there were no increases in energy intake and, after infancy, no residual benefits from past WIC participation; strongest dietary effects among children who were poor, black, or in single-parent or large families (children lost to WIC were as needy as those currently enrolled); shorter stature, suggesting effective targeting (with enrollment in utero there was no parallel deficit in head circumference, which is consistent with results for newborns); better immunization and more frequent regular source of health care but no more frequent use of preventive health services; and better vocabulary with WIC participation begun in utero; better digit memory with entry into the program after the first birthday (differences that emerged only after statistical adjustment for sociodemographic factors); and more advantageous child behavior (NS).