Tubal pregnancy associated with additional conception in a contralateral tube.

Pregnancy of unknown location is defined as empty endometrial cavity despite positive pregnancy test, and often develops as overt intrauterine or ectopic pregnancy. The pathophysiology of persistent pregnancy of unknown location, however, which involves continuous low serum human chorionic gonadotropin without any visible implantation site, is unknown. We report a case of left tubal pregnancy associated with additional conception in the contralateral tube. Left tubal pregnancy was suspected in a 40-year-old nulligravid woman after two embryo transfers following in vitro fertilization. Laparoscopic bilateral salpingectomy was performed for bilateral hydrosalpinx. Products from an additional conception were identified in the right tube. Short tandem repeat analysis using genomic DNA from resected specimens indicated two conceptions of different origin. The extra conception identified on microscopy may indicate one pathogenesis of persistent pregnancy of unknown location. Salpingectomy of the contralateral tube with hydrosalpinx is an option to prevent persistent occult pregnancy.