New medications with no published data are automatically categorized in which lactation risk category?

• A. L2 possibly compatible
• B. L1 compatible
• C. L3 probably compatible
• D. L4 probably contraindicated

Answer: (C)

When there’s no published data on a new medication’s safety in breastfeeding, the default is to categorize it as probably compatible. This middle ground reflects that there’s no evidence of harm to the infant, but there’s also no data confirming safety. It guides clinicians to continue breastfeeding while monitoring the infant and to re-evaluate if new information becomes available. If there were published data showing safety, it would be labeled compatible; if there were data suggesting risk, it would shift toward probably contraindicated; and a lack of data combined with any suggestion of risk would not fit this automatic categorization.