The disappearance of human chorionic gonadotropin from plasma and urine following induced abortion. Disappearance of HCG after induced abortion.
In 28 females, daily measurement of the HCG concentration in urine and in 15 of them daily measurement of the beta-HCG concentration in plasma was carried out during the first 2 weeks following first-trimester induced abortion by vacuum aspiration. Plasma beta-HCG concentration fell according to a multi-exponential curve with a half-life of 0.63 days in the first 2 days following induced abortion, and of 3.85 days in the subsequent 14 days. The disappearance of HCG from urine is exponential, with a half-life value of 1.3 days. A urine pregnancy test with a sensitivity of 1 IU/ml wil nearly always be negative in the course of 2 weeks after abortion. A positive test 4 weeks after abortion indicates an incomplete abortion or persistent trophoblast.