Progesterone production by the ovaries increases when a woman is pregnant, and the level of progesterone can also be a useful indicator of a preterm miscarriage or a poorly established pregnancy. However, progesterone values are not clinically relevant for ruling out ectopic pregnancy. Because progesterone levels are likely to be within the normal range in the early stages of both normal intrauterine pregnancies and abnormal ectopic pregnancies, progesterone levels are not clinically useful in ruling out ectopic pregnancies. The main tests to rule out ectopic pregnancy are the blood HCG, or chorionic gonadotropin, and ultrasound of the uterine adnexa. If the blood HCG value does not increase and the gestational sac is not found in the uterine cavity by ultrasound after 6 weeks of menopause, then ectopic pregnancy is very likely. However, if the progesterone and HCG values continue to decrease, then it is also possible that a spontaneous miscarriage or a biochemical pregnancy may be the cause. If a gestational sac is found in the ovaries, fallopian tubes, etc., on ultrasound, the diagnosis of ectopic pregnancy can be confirmed directly. Sometimes, although the progesterone value cannot definitively exclude ectopic pregnancy, if the progesterone value is lower than 15ng/ml or lower than 5ng/ml, the possibility of ectopic pregnancy is considered, and if the progesterone value is greater than 25ng/ml, the possibility of ectopic pregnancy can be basically excluded.