Longitudinal observations of human chorionic gonadotropin in serum following surgery for ectopic pregnancy

In order to study the disappearance of human chorionic gonadotropin (hCG) in serum after surgery for ectopic pregnancy and to facilitate the postoperative follow-up of hCG decline serial hCG serum concentrations were analysed in 189 women with an uneventful postoperative course and in 4 patients with persistent trophoblast. A double logarithmic transformation of hCG concentrations resulted in a linear relationship of the individual hormonal decline versus the postoperative time (r2 = 0.990). The decrease of hCG levels was independent from the type of surgery or gestational age. The calculated half life of hCG steadily increased with rising time interval after surgery. A nomogram of hCG decrease was constructed using the regression lines of the individual sequential hormone concentrations. The nomogram enabled the detection of active residual trophoblast within one week after surgery before serious complications occur. Our scheme requires only three hCG tests to be performed before surgery, and on day 2 and 7.