every reproductive endo i have seen, as well as MFMs, when they supplement progesterone, they use vaginal suppositories - it doesn't absorb well into the bloodstream, and the pills are just a step above "useless" in their opinions... if progesterone levels are low, yes, a miscarriage can occur. you typically only take them during the first 12 to 13 weeks of pregnancy and then come off of them. progesterone is normally produced in high quantities during the early stages of pregnancy, so it would typically be in your body anyways. i have had 3 miscarriages and 3 live births - my last one i did use the suppositories after 2 consecutive miscarriages and we had a successful pregnancy that time. my husband is a pharmacist as well, and he was totally fine with me taking the suppositories. good luck, and don't be afraid to ask more questions of your doctor - that is what he is for.