Can a Woman Breastfeed Another Woman's Child? Biological Requirements for Lactation

Lactation requires the hormonal milieu of late pregnancy and postpartum: high prolactin, low estrogen/progesterone, and oxytocin release. These changes occur only after gestation and delivery (or with intensive hormonal induction protocols).

A woman who has not been pregnant and given birth (or undergone induced lactation) cannot produce breast milk. Therefore, sisters — or any women — cannot breastfeed each other's children unless they are themselves lactating from a recent pregnancy or a medically supervised induction regimen.

Wet-nursing (breastfeeding another's infant) has historical precedent but requires the nurse to be actively lactating.