It's progesterone, something some people don't make enough of naturally to maintain a pregnancy. I have been on it since the beginning. I had a leep also, and 2 previous complicated pregnancies. To me this means you are going to a cautious Dr who will do everything to help keep your pregnancy safe. I also had a preactionary cerclage and since you had a leep, this may be something else they recommend.
I haven't taken this before but I just looked it up and that's very weird. I would talk to the doc again to make sure. On the bright side if you are taking it I read that the medication is safe during pregnancy so it won't effect the baby