Since progesterone has no known negative effects on pregnancy, and since its relatively cheap, I educate patients about the studies, but do prescribe it for those who want it.
This way, the patient never has to wonder what might have happened if they had taken progesterone.
In pregnancy, how long should my progesterone level be followed?
In almost all cases, as soon as a heartbeat is seen, further progesterone measurements are not useful. The heartbeat can be seen as early as five weeks and six days.
In natural pregnancies, at seven weeks the placenta will make all the progesterone needed for a woman to stay pregnant. Even if you removed the ovaries and stopped all progesterone, the women wont have an increased risk of miscarriage! How do we know this? A study was actually done that showed this!
We routinely give our IVF patients progesterone until around eight weeks of pregnancy, one week beyond this critical week. If a patient wants to stay on longer, fine. No harm should come from it, but its not needed.
Measuring progesterone levels at this point are pointless. If the placenta cant make enough at this point, then the placenta wont be good enough to support the pregnancy and the patient would miscarry anyway.
We would argue that progesterone levels measured after seven weeks, especially if a woman is taking progesterone as a medicine, these levels are providing no real useful information.