Serial monitoring of human chorionic gonadotropin and free beta subunit secretion in ectopic pregnancy

The diagnosis of ectopic pregnancy (EP) has relied primarily on serial serum sampling for human chorionic gonadotropin (hCG) and timely pelvic ultrasound examinations. We recently described the applicability of free beta hCG, intact hCG ratio (%) to distinguish EP from spontaneous abortion or intrauterine pregnancy and found that 35% of EP were uniquely characterized by ratios greater than 0.10. In the present study, we sought to determine if this altered pattern of free beta subunit and intact hCG secretion when present persisted as the EP progressed and whether this ratio was influenced by estradiol (E2) and progesterone (P4) secretion. Twelve patients with histologically-confirmed EP and ratios greater than 0.10 were studied longitudinally from initial presentation to surgical intervention. Ratios (%) ranged from .10 to .52 and persisted at levels greater than 0.10 throughout the period of monitoring in all patients. Intact hCG, free beta hCG and ratios (%) showed no correlation to E2 or P4 concentrations. These data suggest that ratios greater than 0.10 when present persist throughout gestation in EP and may serve as a marker for early diagnosis of EP. Such patterns of hCG secretion in EP may be secondary to altered placental histology with persistence of histologic patterns characteristic of early gestation.