Serum progesterone and human chorionic gonadotropin in very early pregnancy: implications for clinical management

We studied beta-human chorionic gonadotropin (beta-HCG) and progesterone (P) in maternal serum in 71 patients with a positive urine pregnancy test with a threshold of 50 U HCG/liter urine and an ultrasound examination without demonstrable fetal heart beat. Patients were divided into three groups: ongoing intra-uterine pregnancy of more than 12 weeks duration (n = 23), ectopic pregnancy (n = 14), and abnormal intra-uterine pregnancy (blighted ovum, early spontaneous abortion) resulting in dilatation and curettage (n = 34). We found that both beta-HCG and progesterone levels were significantly lower in abnormal pregnancies but that there was less overlap between the progesterone values in normal, ectopic and abnormal pregnancy as compared to beta-HCG levels. There was a positive correlation between beta-HCG levels less than 5000 mU/ml and serum progesterone in ectopic pregnancies but not in normal or abnormal intra-uterine pregnancies. The size of the gestational sac correlated with serum beta-HCG levels but not with serum progesterone levels in normal intra-uterine pregnancies. We conclude that serum progesterone levels (cut-off point 15 ng/ml) in very early pregnancy can be helpful to differentiate between normal intra-uterine pregnancy and abnormal intra-uterine or ectopic pregnancy.