The monstrous mother is a recurring, multifaceted representation of women and their bodies within early modern English literature. Writers of vernacular medical texts sometimes identify monstrous mothers by their breasts, breast milk, and breastfeeding practices. In this essay, I will explain how such texts reflect wider cultural debates about women and potentially expose male anxiety about female corporeal power. Although most texts provide important practical material about women’s breast health and infant nutrition, the assumption of a vein connecting the uterus and breasts afforded several avenues for writers to denigrate lactators and breast milk. Contrasting depictions of the good, natural mother with images of the monstrous mother who produced bad, or corrupted good, milk abound in the texts, some writers alleging that lactators physically and mentally alter infants by transferring disproportionate humours, female fancy, and disease through milk. Further, many authors argue against the use of wet nurses, describing mothers refusing to nurse as unnatural and wet nurses as mercenary. Perhaps the most revealing commentary on monstrous maternity is the appropriation of this normative and vital female corporeal function by testifying to male lactation. These conflicting medical accounts of lactation lay bare early modern questions about women from various cultural perspectives and scientific developments.