The Field Representative's Manuals for 1981, 1985, and 1990 note that breastfeeding includes that given by a wet nurse or if the mother's milk was given to the child through a bottle. The Manual further directs the interviewer to footnote the situation (either "wet nurse," "bottle," or "natural").

In 1981, this variable was part of the child health core questionnaire. 1985 and 1990, this variable was asked as part the Injury Control and Child Safety and Health section. In 1985, the Manual notes that this was part of an effort to collect data to evaluate the effectiveness programs intended to increase breastfeeding. In 1990, this variable was designed to capture data on the practice of preventive measures, such as breastfeeding, to improve child health.