According to the USCIS, WIC is considered a benefit not subject to Public Charge consideration. Therefore, when asked on I-485 if having received public assistance, what should be checked?
The Special Supplemental Nutrition Program for Women, Infants and Children (known as WIC) is a Federal assistance program of the Food and Nutrition Service (FNS) of the United States Department of Agriculture (USDA) for healthcare and nutrition of low-income pregnant women, breastfeeding women, and infants and children under the age of five. (See Child nutrition programs) The eligibility requirement is a family income below 185% of the U.S. Poverty Income Guidelines. If a person participates in other benefit programs, or has family members who participate in the Food Stamp Program, Medicaid, or Temporary Assistance for Needy Families, they automatically meet the eligibility requirements.
In answer to your question, certain non-cash benefits and special-purpose cash benefits that are not intended for income maintenance are not subject to public charge consideration. Examples include Medicaid, Food Stamps and WIC.