Spontaneous resolution of ectopic pregnancy: initial appearance and evolution at transvaginal US.

Spontaneous resolution of ectopic pregnancy (EP) diagnosed with transvaginal ultrasound (US) was confirmed in 13 patients from May 1990 to December 1991. These cases accounted for 24% of the total number of EPs seen in our institution during the same period. These EPs ranged in size from 1 to 3.5 cm, and the beta subunit of human chorionic gonadotropin (beta-hCG) level was less than 1,000 IU/L in all patients. The serum beta-hCG levels became undetectable in 3-45 days (mean, 15.8 days). All EPs had completely resolved at follow-up transvaginal US performed 10-63 days (mean, 30 days) after initial examination. A gestational sac was present in three of these patients, and various degrees of vascularity were detected in four. Four of the resolving EPs increased in size. Four of the nine EPs without detectable flow initially became mildly vascular during the course of resolution. The authors concluded that spontaneous resolution of EP is not an uncommon phenomenon and occurs more commonly in patients with less advanced and less vascular EPs and serum beta-hCG levels less than 1,000 IU/L. EPs can increase in size and become more vascular during their course of resolution.