The five participant categories are defined precisely in 42 U.S.C. 1786(b), and the boundaries matter because they are the commonest reason a family loses coverage without warning. Pregnant women are covered throughout pregnancy. Postpartum women are covered "up to six months after termination of pregnancy". Breastfeeding women are covered "up to one year postpartum" while they are breastfeeding, which is why continuing to breastfeed extends the mother's own eligibility by six months. Infants are people under one year of age. Children are people "who have had their first birthday but have not yet attained their fifth birthday", so eligibility ends on the fifth birthday rather than at the start of school.
Eligibility is a three-part test and all three parts bind. First, the applicant must be in one of those categories. Second, the applicant must meet an income standard. Third, a "competent professional authority" defined at 1786(b)(3) to include physicians, nutritionists, registered nurses, dietitians and certain trained health officials must find nutritional risk, which 1786(b)(8) defines broadly enough to reach anemia, poor weight gain in pregnancy, inadequate dietary patterns, and conditions such as homelessness or migrancy that predispose a person to poor nutrition. Because the risk finding is clinical rather than financial, two families with identical incomes can get different answers.
The income test has two independent routes, and the second one is the reason many working families are eligible without realizing it. Under 1786(d)(2)(A)(i) an applicant qualifies if family income is below the maximum limit for reduced price school meals, which 42 U.S.C. 1758(b)(1)(A) sets at 185 percent of the federal poverty guidelines. Alternatively, under 1786(d)(2)(A)(ii) and (iii), the applicant qualifies automatically by receiving SNAP benefits, by being in a family receiving TANF, by receiving Medicaid, or by being in a family in which a pregnant woman or an infant receives Medicaid. This is usually called adjunctive or automatic income eligibility. Note the precision of the Medicaid route. A school-age child on Medicaid does not make the household income-eligible; a pregnant woman or an infant on Medicaid does.
Two further mechanics sit inside the income test. A pregnant woman whose household is too small to meet the income standard is treated as meeting it if adding one person to the household size would do so, under 1786(d)(2)(D), which counts the pregnancy itself. And a state may treat a pregnant woman who meets the income standard as presumptively eligible and certify her immediately, completing the nutritional risk evaluation within 60 days, under 1786(d)(3)(B). WIC's income guidelines also run on their own calendar. The Federal Register notice setting them is titled by program year rather than calendar or fiscal year, most recently the "2026/2027 Income Eligibility Guidelines" published on April 29, 2026, and they take effect on July 1.
The structural fact that separates WIC from an entitlement program is in the first sentence of the statute. Section 1786(a) authorizes the program "up to the authorization levels set forth in subsection (g)", and it is funded by annual appropriation rather than as a claim any eligible person can enforce. The practical consequence is written into the regulations. Under 7 C.F.R. 246.7(e)(4), when a local agency reaches its maximum participation level, new vacancies are filled from a waiting list using a seven-level participant priority system, with pregnant and breastfeeding women and infants at nutritional risk ranking above older children. Eligibility and enrollment are therefore two different things, and applying early in a pregnancy rather than late is the single most useful thing a prospective participant can do.