Interquartile ranges of longest interfeeding intervals (as indicated by responses to the questionnaire item, “In an average 24-hour period, what is the longest time for you, the mother, between breastfeedings or expressing milk?”) according to breastfeeding type and infant age. Exclusive BF indicates that the infant consumes only breast milk and absolutely no other foods or liquids; BF with formula, the infant consumes breast milk, other foods and liquids, and infant formula; BF without formula, the infant consumes breast milk and other foods and liquids but not infant formula.