Serum human chorionic gonadotropin (hCG) trend within the first few days after medical abortion: a prospective study

To prospectively describe the decline in serum human chorionic gonadotropin (hCG) in the first 5 days after complete medical abortion and evaluate the influence of initial hCG and gestational duration.

We conducted a prospective, physiologic study of women ≤63 days gestation who underwent medical abortion with 200 mg mifepristone and 800 mcg buccal misoprostol. We stratified enrollment into two gestational cohorts, <49 days and 49-63 days, to ensure gestational variability. We collected serum quantitative hCG values on Day 1 (day of mifepristone), Day 3, Day 5 and a routine follow up hCG on Days 7-14. We calculated the percent hCG decline from Day 1 to each repeat measure and evaluated trends based on initial serum hCG level and gestation.

We enrolled 66 women; 59 were protocol-adherent and included in our analysis. Mean gestation on Day 1 was 49 days and mean baseline hCG was 72,332 IU. Fifty-seven subjects (97%) had a complete medical abortion without further intervention. The mean serum hCG decline among subjects with complete medical abortion was 70.0±10.6% [range 36.9-98.6%] on Day 3 and 91.4±4.4% [range 68.4-97.7%] on Day 5. The mean serum hCG decline from Day 1 to routine follow-up on Days 7-9 was 97.1±1.7% [range 92.4-99.2%], from Day 1 to Day 10-11 was 98.5±1.4% [range 94.7-99.6%] and from Day 1 to Day 12-14 was 98.7±2.8% [range 86.7-99.9%]. There was no difference in percent hCG decline stratified by initial hCG or gestation.

There is a rapid and predictable decline in serum hCG as early as Day 5 after complete medical abortion through 63 days gestation. Rate of hCG decline is not affected by initial hCG or gestational duration.

For women who require confirmation of complete abortion sooner than 1 week after mifepristone, due to patient preference, logistical constraints or in the setting of pregnancy of unconfirmed location, a single repeat hCG on Day 5 may be clinically useful.