PEDIATRICS Vol. 119 No. 2 February 2007, pp. 281-289 (doi:10.1542/peds.2006-1486)
ARTICLE |
Special Supplemental Nutrition Program for Women, Infants, and Children and Infant Feeding Practices
a Department of Public Administration and Policy, American University, Washington, DC
b US Government Accountability Office, Washington, DC
c Economic Research Service, US Department of Agriculture, Washington, DC
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ABSTRACT |
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 TOP ABSTRACT BACKGROUNDMETHODSRESULTSDISCUSSIONREFERENCES |
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OBJECTIVE. This study examined the association between participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and adherence to 4 American Academy of Pediatrics recommendations on infant feeding.
METHODS. We used data from the Early Childhood Longitudinal Study-Birth Cohort, which is nationally representative of children born in 2001. We estimated regression models to assess relationships between program participation and adherence to American Academy of Pediatrics recommendations on exclusive breastfeeding and the introduction of infant formula, cow's milk, and solid foods.
RESULTS. Regression results indicated that WIC participation was associated with a 5.9-percentage point decrease in the likelihood of exclusive breastfeeding for 
4 months and a 1.9-percentage point decrease in the likelihood of exclusive breastfeeding for 6 months. Program mothers were 8.5 percentage points less likely than nonparticipants to adhere to the American Academy of Pediatrics recommendation to delay introduction of infant formula until month 6. Program mothers were 2.5 percentage points more likely than nonparticipants to delay the introduction of cow's milk until month 8. Program participants were 4.5 percentage points less likely than nonparticipants to delay the introduction of solid foods for 4 months. However, the difference between participants and nonparticipants disappeared by month 6.
CONCLUSIONS. Results suggest that, although program participants are less likely to breastfeed exclusively than eligible nonparticipants, program-provided infant formula is an important option for mothers who do not breastfeed exclusively. The program faces the challenge to encourage breastfeeding without undermining incentives to follow other recommended infant feeding practices. Recent changes proposed to the food packages by the US Department of Agriculture Food and Nutrition Service are consistent with the goal of increasing adherence to recommended infant feeding practices among participants.
Key Words: breastfeeding • guidelines • demographic characteristics • infant feeding • WIC • Special Supplemental Nutrition Program for Women • Infants • and Children
Abbreviations: AAP—American Academy of Pediatrics • ECLS-B—Early Childhood Longitudinal Study-Birth Cohort • WIC—Special Supplemental Nutrition Program for Women, Infants, and Children
The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides nutritious foods, nutrition counseling, and referrals to health services and other social services to low-income women, infants, and children up to age 5. WIC was established as a pilot program in 1972 and has grown from serving an average of 88000 participants in 1974 to an average of 8 million in 2005. The congressionally appropriated funding for WIC was almost $5 billion during 2005, up from $10.4 million during its inaugural year, reflecting dramatic increases in participation and spending per participant.1 Approximately one fourth (1.9 million) of WIC participants are pregnant or postpartum women.2
Through the composition of its food packages and provision of nutritional counseling, WIC may influence the infant feeding decisions of its participants. Infant feeding practices are an important determinant of maternal and child health outcomes,3–14 which underscores a need to understand WIC's influence on them. With the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B), this study examines the influence of WIC participation on adherence to recommendations by the American Academy of Pediatrics (AAP) concerning the following 4 infant feeding practices: the persistence of exclusive breastfeeding and the introduction of infant formula, cow's milk, and solid foods.
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BACKGROUND |
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Recommended Infant Feeding Practices
Among the various forms of infant nourishment, breast milk is widely considered to be the most nutritionally beneficial during the postpartum period.3 Breast milk contains immunologic agents that protect infants against infectious diseases such as bacterial meningitis, diarrhea, respiratory ailments, and urinary tract infections.4,5 Breastfeeding also has a positive impact on maternal health, including quicker return to prepregnancy weight6 and reduced incidence of breast and ovarian cancer.7–9 The social benefits of breastfeeding include lower national health care costs and reduced costs to government programs such as Medicaid and WIC through promotion of healthier mothers and infants.10
Given the benefits of breastfeeding, the AAP Work Group on Breastfeeding recommends exclusive breastfeeding for the first 6 months of an infant's life.13 The AAP defines exclusive breastfeeding as feeding infants solely breast milk, without any form of supplementation. During the second 6 months of an infant's life, the AAP recommends that breastfeeding continue, supplemented with other nutritional sources.
Infant formula, although not as nutrient-rich as breast milk, contains nutrients that are important for positive health outcomes. The high iron content in iron-fortified formula aids in infant growth and development while reducing the risk of iron-deficiency anemia, which can cause abnormal cognitive, social, and motor skill development.15 Cow's milk, in contrast, is low in iron and often is difficult for infants <9 to 12 months of age to digest.11 The AAP recommends that infants being weaned from breast milk, and those who are not breastfed, receive iron-fortified formula instead of cow's milk. Although continued breastfeeding is desirable throughout the first year, the guidelines allow for weaning after 6 months, implying that mothers should refrain from introducing infant formula until at least that age. The AAP advises all mothers explicitly to abstain from introducing cow's milk until their child is 12 months of age.
The AAP Work Group on Breastfeeding recommends introduction of solid foods at 6 months of age,13 noting that solid foods are not necessary for optimal growth until month 6 and that their introduction may cause substitution away from human milk, which continues to provide protection against diarrhea and respiratory tract infections. In addition, some research suggests that delaying the introduction of solid foods until month 6 decreases the probability of allergic reactions to food, such as asthma and eczema, during childhood.14 There are experts, however, including the AAP Committee on Nutrition, who support the introduction of complementary foods to infants 4 to 6 months of age who are developmentally ready.12
WIC and Infant Feeding Practices
WIC provides different food packages to mother/infant pairs, depending on whether the infant is breastfeeding or not. Nonbreastfed infants receive infant formula up to their first birthday. Concerns have been raised that the supply of infant formula may discourage breastfeeding among WIC participants. Therefore, since the 1990s, WIC has increased its emphasis on breastfeeding promotion.16 The WIC food packages have also been revised to reduce the difference in the market value of the package provided to participants who breastfeed and those who do not.17 All WIC infants receive infant cereal from 4 to 12 months of age.18
Research has shown that WIC participants are less likely to breastfeed, with or without supplementation, than nonparticipants.19–29 Recent studies used a variety of sophisticated empirical strategies to examine whether this disparity in any breastfeeding is attributable to WIC participation itself or to other characteristics associated with WIC participation.20,22–24
Unlike the studies examining the relationship between WIC participation and any breastfeeding, research on WIC and AAP-recommended infant feeding practices has focused on descriptive comparisons of WIC participants and nonparticipants. However, data limitations constrain their ability to identify precisely those who are eligible for WIC, an important comparison group. The studies are also constrained in the extent to which they can control for the numerous other factors that could influence a mother's decision to breastfeed exclusively.
Three studies found that WIC participants were less likely to breastfeed exclusively than nonparticipants.27–29 Previous analyses found that WIC participation was associated with greater reported use of infant formula29,30 or with higher intake of iron, which was attributed to the use of iron-fortified infant formula.21,29,30 Most research found that WIC infants were less likely than eligible nonparticipants to consume cow's milk, on the basis of reported feeding patterns30,31 and nutrient intake analysis.21,30,32 One exception was Ponza et al,29 who found no difference between WIC and non-WIC infants 7 to 11 months of age with respect to the introduction of cow's milk. They did find that WIC infants 4 to 6 months of age were more likely to have been fed cow's milk than were non-WIC infants, although introduction of cow's milk was quite rare in both groups. As noted previously, the non-WIC infants included those who were not eligible to receive WIC benefits.
Although an early study found that WIC participants were more likely to delay the introduction of solid foods until the child was 4 months of age,30 more-recent studies found no difference between WIC participants and nonparticipants.29,31 There is some evidence that WIC participants are less likely to introduce solid foods to infants 4 to 11 months of age,32 but it is not possible to determine whether the difference exists in the 4- to 6-month period relevant to the AAP infant feeding recommendations.
Previous research provided valuable descriptive information regarding the association between WIC participation and recommended infant feeding practices. This study contributes to this body of research in several dimensions. First, the study examines the relationship between WIC and 4 infant feeding practices that have received significantly less attention than any breastfeeding. This study uses recent, nationally representative data that are comparable to other nationally representative data sets for breastfeeding outcomes.28 These data provide rich socioeconomic information, so that we can determine who is eligible for WIC and compare WIC participants with those who are eligible but do not participate. Finally, we estimate regression models and control for a variety of factors in an attempt to isolate the effect of WIC participation on adherence to recommended infant feeding practices.
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METHODS |
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Data Set
The data set used in this analysis was the ECLS-B. The ECLS-B is a longitudinal data set collected by the National Center of Education Statistics. The baseline sample of 10688 children was designed to be nationally representative of children born in 2001. The data set contains oversamples of children who are American Indian, Chinese, members of another Asian or Pacific Islander group, are twins, or were born with low or very low birth weight. The first wave of data contains information from the child's birth certificate and information on the child and his or her parents from a household survey administered
9 months after the child's birth. The ECLS-B contains rich information on children's health status, growth and development, and school readiness. Pertinent to this study, the ECLS-B contains information on WIC participation, breastfeeding and other infant feeding practices, demographic characteristics, income and assets, participation in other assistance programs, and health status and behaviors.
To perform our analysis, we constructed an analysis sample of 5276 eligible mothers. Mothers needed to meet the following 6 inclusion criteria, with the number of observations excluded for each criterion as noted. First, only observations with state identifiers were included in the analysis (86 observations excluded). Second, only biological mothers were included (141 observations excluded). Third, mothers with multiple births were included as single observations (794 observations excluded). Fourth, only mothers whose survey child was 8 months of age and <18 months of age at the time of the assessment were included (96 observations excluded). Fifth, only observations with complete information for all relevant variables, with the exception of the variable indicating that the child was firstborn, were included (773 observations excluded). There were >200 observations with missing data on whether the child was firstborn; therefore, we assigned them a value of 0, the modal value, for the firstborn indicator and included a variable that indicated whether the observation was missing data for that variable. Finally, only mothers who were eligible for WIC were included (3522 observations excluded). To be eligible, a mother must have household income of <185% of the poverty level or participate in the Food Stamp Program, cash welfare, or the Medicaid program. In addition, she must be determined to be at nutritional risk. Although the ECLS-B does not include data to allow determination of whether a woman is at nutritional risk, research has found that nearly all income-eligible individuals are also at nutritional risk.33
Among eligible mothers in our analysis sample, 80.6% participated in WIC, and 66.7% began participating during pregnancy (Table 1). Eligible mothers who chose to participate seemed to be more disadvantaged than those who did not participate. Mothers who participated in WIC were more likely to be non-Hispanic black or Hispanic, to have less than a high school education, to be younger, to have never been married, to participate in other assistance programs, and to have incomes below the poverty level, compared with their nonparticipant counterparts.
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Statistical Analyses
We estimated probit models, with dependent variables that captured the infant feeding practices recommended by the AAP. Each mother responded to questions that asked the age of the child (in months) when she began feeding her infant formula, cow's milk, or solid foods. Exclusive breastfeeding was defined as refraining from feeding infant formula, cow's milk, and solid foods. Survey respondents did not provide information about feeding their infants other liquids, such as water or juice. Although our definition of exclusive breastfeeding was not as restrictive as that used by Li et al28 in their analysis of the National Immunization Survey, the exclusive breastfeeding rates among all women were quite consistent. We examined the introduction of solid foods (and exclusive breastfeeding) at both 4 and 6 months because of the variation in the recommendations regarding the introduction of complementary foods. Adherence to cow's milk recommendations was measured at 8 months instead of 12 months because most of the infants surveyed were not yet 12 months of age at the time of the assessment.
The primary independent variable of interest, WIC participation, was defined as the mother having received WIC benefits during pregnancy, during the first 6 months after pregnancy, or having received WIC vouchers to purchase food or formula for her infant in the 30 days before the survey. Along with the dichotomous WIC participation variable, we included many of the characteristics thought to be associated with infant feeding decisions as control variables. The characteristics presented in Table 1 were included as explanatory variables. These variables included mother's race and ethnicity (with non-Hispanic white as the basis), mother's education (with no high school diploma as the basis), mother's age (with age of <20 years as the basis), mother's primary language (with English as the basis), mother's relationship status (with married as the basis), the presence of other children <5 years and between 5 and 17 years of age, whether the mother has twins, and whether the interview child is the mother's first. We also included indicator variables for the region of residence (with residence in the West as the basis) and for living in an urban area.
We captured the women's experience with other assistance programs with an indicator variable for participating in cash welfare, the Food Stamp Program, or Medicaid since the birth of the child and 2 variables for the amount of time (some of the time or at least most of the time) the household received cash welfare during the mother's childhood (with no cash welfare receipt as the basis). We also included household income, an indicator variable for household income below the poverty level, and an indicator variable for being employed any time during the 12 months before the child's birth. We characterized the woman's assets with indicator variables for home ownership, car or truck ownership, having investments, and having a savings or checking account.
Variables to describe characteristics related to the women's pregnancy and general health were also included in the analysis. We controlled for differences in prenatal care by including indicator variables for whether prenatal care was paid for by Medicaid, was paid for by some other means, or was not received at all (using prenatal care paid for by private insurance as the basis). We also included a variable for the number of weeks into her pregnancy when the mother found out she was pregnant, a variable that indicated that the woman had smoked 100 cigarettes during her lifetime, and a variable that indicated whether the mother had smoked during her third trimester.
All probit regressions were weighted by using the weight variable W1RO, which was provided with the ECLS-B data. Marginal effects evaluated with the means of the independent variables are presented. Estimated marginal effects of WIC participation in unweighted regression analyses (available from the authors on request) are quite similar to those reported. SEs were adjusted to correct for heteroskedasticity.
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RESULTS |
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TOPABSTRACTBACKGROUNDMETHODSRESULTSDISCUSSIONREFERENCES |
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Descriptive analysis showed that 44% of WIC participants and 59% of nonparticipants exclusively breastfed through the first 1 month after childbirth (Table 2). Rates of exclusive breastfeeding decreased steadily after the first month. At month 4, 15% of WIC participants and 30% of nonparticipants exclusively breastfed; only 5% of WIC participants and 10% of nonparticipants met the stricter AAP guideline of 6 months. Although the rates of exclusive breastfeeding among all mothers in the ECLS-B were quite consistent with those produced by using the National Immunization Survey,28 we found lower rates of exclusive breastfeeding among WIC-eligible mothers. This was likely attributable to differences in calculating both WIC eligibility and WIC participation.
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The estimated marginal effects of WIC participation on infant feeding practices from the probit regression analysis are presented in Table 3. Coefficients for control variables for the exclusive breastfeeding models generally had the expected signs. Full regression results for 4 of the models are presented in the Appendix. Our regression analyses of exclusive breastfeeding (Table 3) showed that WIC participation was associated with a 5.9-percentage point decrease in the likelihood of exclusive breastfeeding for
4 months (P < .01) and a 1.9-percentage point decrease in the likelihood of exclusive breastfeeding for 6 months (P < .05). The negative association between WIC participation and exclusive breastfeeding is consistent with results from other studies.27,28 However, our regression results indicated that the magnitude of the negative relationship decreased when we controlled for other characteristics that influence exclusive breastfeeding.
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As shown in Table 2, WIC mothers were more likely to initiate infant formula feeding during the first 1 month after child birth (56%, compared with 41% of nonparticipants). By month 6, 88% of participants and 72% of nonparticipants had introduced infant formula. Regression results indicated that WIC mothers were 8.5 percentage points less likely than non-WIC mothers (P < .01) to adhere to the AAP recommendation to delay introduction of infant formula until month 6 (Table 3). The negative association between WIC participation and delaying the introduction of infant formula until 6 months after birth is consistent with previous studies.29,30 Consistent with our finding on exclusive breastfeeding, the regression results indicated that the measured association between WIC participation and infant formula feeding was much smaller when we controlled for other explanatory factors.
Although WIC mothers were less likely to delay the introduction of infant formula than non-WIC mothers, they were more likely to delay the introduction of cow's milk. It was not common for either WIC participants or nonparticipants to provide cow's milk to their infants, with <4% of eligible women introducing it by month 8. Regression results suggested that WIC mothers were 2.5 percentage points more likely (P < .01) to delay the introduction of cow's milk until month 8 than were nonparticipants (Table 3). The finding that WIC participants were more likely to delay the introduction of cow's milk is consistent with most previous research.21,30–32
The descriptive analysis illustrated that WIC participants were more likely than nonparticipants to introduce solid foods to their infants by month 4 (Table 2). Our regression results corroborated the descriptive analysis. WIC participants were 4.5 percentage points less likely than nonparticipants (P < .05) to delay the introduction of solid foods until their infant was 4 months of age (Table 3). This finding is in contrast to previous studies on the association between WIC participation and introduction of solid foods before month 4.29–31 However, the difference between WIC participants and nonparticipants disappeared by month 6 (Table 3), which is consistent with previous studies.29,31
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DISCUSSION |
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TOPABSTRACTBACKGROUNDMETHODSRESULTSDISCUSSIONREFERENCES |
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WIC participation is related to most, but not all, of the infant feeding decisions of eligible mothers. WIC participation is associated with a lower likelihood of exclusive breastfeeding and a greater likelihood of infant formula introduction. Combined with WIC participants' lower likelihood of introducing cow's milk prematurely, this finding suggests that WIC-provided infant formula serves as an important nutritional option for mothers who decide to breastfeed partially or not to breastfeed at all. As discussed earlier, infant formula is not as beneficial as breast milk. However, studies show that formula is the second best form of infant nourishment and is nutritionally superior to cow's milk. The relatively high market price of infant formula would likely make such a feeding practice prohibitive for many low-income mothers. Therefore, if WIC stopped offering infant formula, then many nonbreastfeeding WIC mothers might opt to feed their infants less-nutritious alternatives, including cow's milk.
There was also a significant negative relationship between WIC participation and adherence to the recommendation to delay solid foods until the infant is 4 months of age. However, that relationship disappeared at 6 months, and a large majority of eligible mothers had introduced solid foods by that time.
Limitations of the study should be noted. Given that mothers elect to participate in the WIC program, it is difficult to determine the causal effect of WIC participation on infant feeding practices. Several recent studies documented a wide array of differences between eligible mothers who participate in WIC and those who do not.20,22,23,34 Although we have included a rich set of control variables, it is still possible that unobservable characteristics of the mother are associated with both her decision to participate in the WIC program and her infant feeding practices. If so, we may attribute, for example, a lower rate of exclusive breastfeeding to WIC participation when it is attributable to other characteristics that are associated strongly with WIC participation.
Two additional limitations of the study are related to the data collection procedures. First, it was necessary to exclude mothers of infants >18 months of age because we could not ascertain their WIC participation status. Second, our definition of exclusive breastfeeding allowed the provision of juice or water, because we were unable to account for these infant feeding practices in the ECLS-B. Therefore, we might have overestimated the number of infants who were exclusively breastfed.
The promotion of recommended infant feeding practices remains a challenge for WIC, particularly because program participants have characteristics that are associated with a decreased likelihood of adherence to recommended infant feeding practices. The US Department of Agriculture Food and Nutrition Service, which administers the program at the federal level, recently proposed revisions to the WIC food packages,35 largely based on recommendations by the Institute of Medicine.36 Some of the proposed changes would more closely equate the market value and nutritional value of the food packages provided to breastfeeding and nonbreastfeeding women and would provide infant cereal to WIC infants at 6 months, rather than 4 months, of age. These changes are consistent with the goal of increasing adherence to AAP guidelines on infant feeding practices among WIC participants.
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ACKNOWLEDGMENTS |
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We thank Steven Putansu for excellent research assistance. We also thank the participants in an Economic Research Service seminar and the 2006 Food Assistance and Nutrition Research Program conference for their comments.
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FOOTNOTES |
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Accepted Oct 2, 2006.
Address correspondence to Laura Tiehen, PhD, Economic Research Service, USDA, 1800 M St NW, Room S2076, Washington, DC 20036. E-mail: ltiehen{at}ers.usda.gov
The views and opinions expressed in this article do not necessarily reflect the views of the Economic Research Service of the US Department of Agriculture or the US Government Accountability Office.
The authors have indicated they have no financial relationships relevant to this article to disclose.
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