Will Pregnancy Affect My Milk Supply?

I’m newly pregnant and still determined to breastfeed, but I’m a little anxious about this. Will my current pregnancy affect my breast milk supply at all? Does breastfeeding impact anything about my pregnancy? I really want to do what’s best for both my baby and the one on the way.

— Nadine

Let’s start with the second question. People are sometimes told to quit breastfeeding either before becoming pregnant or while pregnant because of concerns about the impact on the fetus. In places where adequate nutrition is not readily available, it is possible that this is an issue. However, for women with adequate nutrition, breastfeeding during pregnancy is not a concern.

A 2017 review article argued that breastfeeding during pregnancy did not impact how the pregnancy ended (i.e., did not affect miscarriage rates) or birth weight. The birth weight results in particular are reassuring since the major worry with nursing during pregnancy is limited nutrients, which could affect birth weight. This reinforces the view that when mom is well-nourished, this isn’t a concern.

To your first question, though, it is likely that your milk supply will decline during pregnancy. Estimates suggest that this happens for about two-thirds of women, with a smaller share having their supply disappear completely. This is most likely to happen mid-pregnancy. The composition of breast milk also changes somewhat toward the middle and end of pregnancy, which may make it less appealing to the infant.

The upshot: if breastfeeding is working for you and your older child during pregnancy, by all means, continue. But do be prepared for the possibility that your older child will choose to wean, or your supply will decrease to the point where that happens naturally.