Discussion of the behaviour of pregnant women and mothers, in academic literature, medical advice given to mothers, mainstream media and social media, assumes that a mother who fails to do something to benefit her child is liable for moral criticism unless she can provide sufficient countervailing considerations to justify her decision. I reconstruct the normally implicit reasoning that leads to this assumption and show that it is mistaken. First, I show that the discussion assumes that if any action might benefit her child, the mother has a defeasible duty to perform that action. I suggest that this assumption is implicitly supported by two arguments but that each argument is unsound. The first argument conflates moral reasons and defeasible duties; the second misunderstands the scope of a defeasible duty to benefit. This argument has important practical and theoretical implications: practically, it provides a response to a highly damaging discourse on maternal behaviour; theoretically, it provides the framework for a clearer understanding of the scope and nature of defeasible duties to benefit.