This study measured the effect of participation in the
Supplemental Nutrition Program for Women, Infants,
and Children (WIC) after the birth of a child on one
important health behavior: the initiation and persistence
of breastfeeding. In the United States, many low-income
mothers do not initiate breastfeeding at all and very
few breastfeed for at least 4 months, although most
pediatricians recommend breastfeeding exclusively for
at least 4 to 6 months. Recognizing this problem,
during the 1990s, the U.S. Department of Agriculture
implemented many new policies intended to promote
and support breastfeeding among WIC participants.
While the new policies promote breastfeeding, the
program provides infant formula in food packages, a
major incentive for mothers to participate in WIC. The
provision of infant formula in WIC food packages may
work against the program’s emphasis on breastfeeding.
To build on previous research on breastfeeding among
WIC participants, this study used data from the children
of the National Longitudinal Survey of Youth—a
large, longitudinal data set that includes children born
between 1990 and 1995. Average annual expenditures
on breastfeeding education and promotion increased
from $9 million in 1990 to $36 million in 1995. The
authors employed econometric methods to account for
self-selection into the WIC program and linked
mothers’ breastfeeding practices to State WIC and
Medicaid policies.
Very little is known about the effect of WIC participation
on breastfeeding practices among participants
during the 1990s. Previous research suggests that a
woman’s participation in WIC during pregnancy leads
to important health benefits for children, including
increases in birth weight, reductions in iron deficiency
anemia, and reductions in infant mortality. Much less
is known, however, about the benefits of WIC participation
after pregnancy, during infancy, and during
early childhood. Although research on the effectiveness
of the WIC program focuses almost exclusively
on a woman’s participation during pregnancy, most
WIC participants are not pregnant women, but rather
are infants, young children, and post-partum women.
A large proportion of WIC funds are targeted at these
groups, but little is known about whether WIC
improves health behaviors and outcomes for them.
This information is necessary to evaluate the overall
effectiveness and cost-effectiveness of the program, as
well as to better target existing funds.
The main empirical challenge in this study was to
account for the possibility that women select into WIC
based on unobservable characteristics that also determine
breastfeeding practices. For example, mothers
disinclined toward breastfeeding might be more likely
to participate in WIC. In this case, standard estimation
methods will lead to a biased and inconsistent estimate
of the effect of WIC on breastfeeding. The authors
used three methods to account for this problem:
- They estimated standard probit models with a rich
set of covariates intended to capture many factors
associated with breastfeeding decisions.
- They estimated the models using an instrumental
variables approach with State-level WIC and
Medicaid policies as identifying instruments.
- They took advantage of data available on siblings
to estimate heteroscedastic, family-level fixed
effects models that control for differences across
families in unobservable characteristics.
The results of the study suggest that WIC participation
has a negative effect on initiating breastfeeding, but it
is not clear whether the program affects breastfeeding
persistence. Baseline results, which are preferable to
instrumental variables results, indicate that WIC
participation has a strong, negative effect on breastfeeding
initiation, but no effect on breastfeeding for at
least 16 weeks. A heteroscedastic fixed-effects model
suggests that within families, WIC participation is
associated with fewer weeks of breastfeeding. It is
important to note that these results are based on a
sample of mothers who are older and probably more
advantaged than the national WIC population. It is also
important to note that expenditures on WIC
breastfeeding education and promotion have increased
significantly since 1995, which would be expected to
influence the effect of the program on breastfeeding.
To generate implications for policy, more qualitative
and quantitative research is needed that confirms the
results from this small body of work. However, if these
results can be replicated using other data, they imply
that, while WIC has the potential to affect infant
feeding practices, the program faces the challenge of
increasing breastfeeding rates among participants,
while continuing to offer infant formula to mothers
who decide not to breastfeed.
