Levels of contraceptive steroids in breast milk and plasma of lactating women

Hormonal contraceptives have been used in breast feeding women by many clinicians. However, secretion of these drugs in the breast milk has not been adequately investigated. In the present study, radioimmunoassay methods were used for estimating the contraceptive drug levels in breast milk and plasma samples. In 7 lactating women, after the injection of 150 mg medroxyprogesterone acetate = MPA (Depo-Provera), MPA levels in breast milk were similar to plasma; the ratio being almost 1: 1 throughout the study period (up to 87 days). In a group of women using oral pills (2 women took a combination pill containing 150 μg d-norgestrel (d-Ng) and 30 μg ethinylestradiol, another 5 women took progestogen-only pills containi 350 μg norethisterone (NET)), the levels of d-Ng and NET in breast milk were about 1/10th or less than those found in plasma.