Which of the following birth control methods is contraindicated for breastfeeding mothers?

Low-dose oral contraceptives that contain estrogen, such as those with at least 20 mcg of estradiol, are contraindicated for breastfeeding mothers due to the potential impact on milk supply. These hormonal contraceptives can interfere with lactation and may lead to decreased breast milk production.

In contrast, progestin-only methods, such as progesterone-only pills (Micronor), do not adversely affect milk production and are therefore considered safe for breastfeeding mothers. Barrier methods like condoms and the diaphragm with spermicidal gel do not influence hormonal levels and have no negative impact on breastfeeding. Thus, the preference for breastfeeding mothers is to use contraceptive methods that avoid estrogen to ensure optimal milk supply and breastfeeding success.