Early and late half-life of human chorionic gonadotropin as a predictor of persistent trophoblast after laparoscopic conservative surgery for tubal pregnancy

BACKGROUND: To determine if the early or late half-lives (T0.5) of human chorionic gonadotropin (hCG) can identify patients with persistent trophoblastic activity after conservative surgery for tubal pregnancy. DESIGN: Prospective cohort study. SETTING: Department of obstetrics and gynecology of a university hospital. METHODS: All patients with a tubal pregnancy treated by laparoscopic salpingostomy between June 1997 and September 2000 were enrolled in the study. Postoperative sequential hCG sampling was performed at days 0, 2 (+/- 1) and 7 (+/- 2) and followed until levels were undetectable. Taking the biexponential hCG declining curve as a model, we calculated the early (days 0-2) and late (days 2-7) T0.5 hCG values. MAIN OUTCOME MEASURE: To assess success or failure of surgical treatment. RESULTS: Seventy-three patients with an ectopic pregnancy were managed by conservative surgery. Early and late T0.5 allowed us to identify 2/10 and 9/10 women, respectively, with persistent trophoblast. Late T0.5 levels revealed two patients with false-positive values, but one patient showed a secondary increase in hCG after day 7 (false-negative) despite a normal late T0.5. CONCLUSIONS: Early and late half-lives of hCG do not identify all women at risk for persistent ectopic pregnancy. To exclude persistent trophoblast, postoperative serum hCG determination should be performed until levels are undetectable.