Progesterone helps to build up the lining of the uterus to receive a fertilized egg, explains WebMD. Progesterone levels rise during ovulation, and a pregnant woman's body produces 10 times more progesterone than a non-pregnant woman does.
During the first trimester of pregnancy, the ovaries produce progesterone, and the placenta takes up the task during the ninth or 10th week of pregnancy, notes About.com. There is some evidence that women who miscarry produce lower levels of progesterone than average prior to miscarriage. However, studies suggest that progesterone supplements do not dramatically decrease the incidence of miscarriage in at-risk patients, and some doctors feel that the supplements delay rather than prevent miscarriage. Some researchers suggest that the lower progesterone levels in patients who suffer miscarriage do not precipitate the miscarriage but rather result from it. There does appear to be some benefit to progesterone supplements for women with a history of three or more miscarriages, and doctors recommend progesterone supplements in the case of assisted reproductive technology such as in vitro fertilization.
Progesterone tests are a useful tool for doctors to determine causes of infertility, monitor fertility treatment, identify ovulation times and determine the potential for miscarriage, reports WebMD. Adrenal gland issues and some types of cancer can also affect progesterone levels.