A regular menstrual cycle, with periods every 28 days on average, and a progesterone value of 25ng/ml or more at 47 days of pregnancy is considered normal. If a woman has an irregular menstrual cycle, with periods coming every 40 days or so, a blood test for progesterone may drop and also be above 15ng/ml. If the value of progesterone is below 15ng/ml, there may be cases of pre-eclampsia such as lower abdominal pain and vaginal bleeding, and if the progesterone is below 6ng/ml, there is a possibility of biochemical pregnancy or embryonic abortion or spontaneous miscarriage. In the early stages of pregnancy, not only the progesterone level but also the HCG level will increase, which can help to determine the growth and development of the embryo in the early stages.