Medical abortion in lactating women – low levels of mifepristone in breast milk

Abstract

OBJECTIVE: Medical abortion using mifepristone followed by misoprostol is increasingly used for termination of an unwanted pregnancy. Consequently, an increasing number of women undergo medical abortion while still breastfeeding from a previous pregnancy. But there are no data on mifepristone use during lactation. We studied the levels of mifepristone in breast milk collected from women undergoing medical abortion. DESIGN AND SAMPLES: Samples of milk were collected from 12 women during the first 7 days after intake of either 200 mg (n = 2) or 600 mg (n = 10) of mifepristone. In addition, serum samples were collected on day 3 (n = 4). Main outcome measures. The levels of mifepristone, quantified using radioimmunoassay. RESULTS: The milk concentrations of mifepristone were highest in the first samples collected during the first 12 hours following drug intake, and ranged from undetectable (< 0.013 micromol/l) to 0.913 micromol/l. Thereafter, declining concentrations of mifepristone were detected up to 7 days. The lowest levels of mifepristone in milk were measured following ingestion of the 200 mg dose. The milk:serum ratio of mifepristone ranged from < 0.013:1 to 0.042:1 on day 3 (n = 4). The calculated relative infant dose (RID) was 1.5% at its highest. CONCLUSIONS: The levels of mifepristone in milk are low, especially when using the 200 mg dose. Breastfeeding can be safely continued in an uninterrupted manner during medical abortion of this kind.