Most sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy.[1] It might be possible to breastfeed safely with busulfan during intermittent therapy with an appropriate period of breastfeeding abstinence. Although minimal data are available to determine an appropriate period to withhold breastfeeding, the drug's terminal half-live of 2.5 hours suggests that at least 24 hours may be sufficient. Chemotherapy may adversely affect the normal microbiome and chemical makeup of breastmilk.[2] Women who receive chemotherapy during pregnancy are more likely to have difficulty nursing their infant.[3]