Lisa, I suspect others will have more info on this than what I found in the 92 USPDI that said that the class of progestin-type drugs appear in the milk in varying quantities and it isn't known whether it matters so they are generally not recommended. I do have a personal anecdote on the subject though. In 1985 I miscarried very early in the pregnancy (about 5 weeks or so--just long enough to register positive on the pregnancy test). It was suspected (though tests failed to confirm it) that it was a progesterone problem. When I got pregnant again, the OB checked blood levels of progesterone and found them low and so started me on the stuff. My son was just 3 and still nursing once or twice a day to go to sleep. I THINK I told the OB that I was still nursing at the time and I seem to recall him not finding that reason for worry. (He was a bit amused that I was still nursing a 3 year old, though!) I had to go in for weekly blood tests for the next 10 weeks or so, and my blood levels of progesterone did not get past pre-pregnant levels until about the 12th week or so. These tests were extremely nerve racking since I never knew from week to week whether I would still be pregnant the next. (I miscarried once before Dan was born as well.) At 12 weeks the OB decided to try consecutive quantitative HCG tests to make sure the levels were still rising. They plummeted. So he tried an ultrasound and I saw my daughter moving! He did some research later and told me that the HCG levels are supposed to drop in the second semester (I don't think he ever had reason to do the tests that far in a pregnancy before). Anyway, to cut a long nightmare of a pregnancy short, Merrilee arrived a few months later, right on schedule. Meanwhile, Dan quit nursing about the time that the progesterone levels came up to where they were supposed to be. I have often wondered whether little nursing he was doing could affect my progesterone levels. I am a DES daughter as well, and have wondered whether that had anything to do with the crazy hormone levels. It did make me a little nervous to be taking a hormone while I was pregnant, and hope that they do not discover 30 years from now any long reaching effects on mom or daughter from that. I don't believe she would be here if I didn't take it though. And will they find long term affects for nurslings of moms taking it? I don't know that any of this answers your question; it is something I wonder about from time to time. Strange the legacies we can unwittingly leave our children.... Melissa Vickers, IBCLC [log in to unmask]