Why is estrogen not recommended for breastfeeding women during early postpartum?

Estrogen is not recommended for breastfeeding women during the early postpartum period primarily because it may decrease milk supply. During this time, the hormones responsible for establishing and maintaining lactation, particularly prolactin, play a critical role. Estrogen can interfere with the prolactin response needed for milk production, potentially leading to a decrease in the quantity of milk a breastfeeding mother can produce.

In contrast, the other options suggest outcomes where estrogen either positively affects milk supply or has no effect, which does not align with the understanding of hormonal influences on lactation dynamics. Therefore, it is crucial for new mothers who are breastfeeding to be cautious about the use of estrogen-containing medications until their milk supply is well established.