Further observations on serial human chorionic gonadotropin patterns in ectopic pregnancies and spontaneous abortions

The half-life of hCG was measured retrospectively in paired blood samples from 108 pregnancies with falling hCG levels. hCG levels fell significantly more slowly in women who had an ectopic pregnancy (41 cases) than in women who had spontaneous abortions (67 cases). When the hCG half-life was greater than or equal to 7 days, 86% of cases had ectopic pregnancies, a third of which had ruptured. By contrast, when the hCG half-life was less than 1.4 days, only 7.6% (2/26) of cases had an ectopic pregnancy (both of which were unruptured), and villi were identified in only 10% of curettage specimens from (presumed) cases of spontaneous abortion. When the half-life of hCG was between 1.4 and 6.9 days, 34% of the cases had ectopic pregnancies, 14% of which had ruptured: chorionic villi were recovered from 76% of the women who had a curettage, and failure to detect villi was more than 80% predictive of an ectopic pregnancy.