Tubal superfetation following frozen-thawed single-embryo transfers in two separate cycles: Case report and literature review

Superfetation is a very rare occurrence. In the context of assisted reproduction, it has been reported only as an intrauterine pregnancy after ovarian stimulation and/or embryo transfer in the presence of an undiagnosed ectopic pregnancy. Here we report a case of a 27-year-old anovulatory patient, gravida 1 para 1, who underwent two frozen-thawed single-blastocyst transfers in separate cycles. The patient reported that 12 days after the first transfer, she had menstrual bleeding and stopped her estradiol and progesterone supplementation without undergoing a blood human chorionic gonadotropin (beta hCG) test. At her request, a second cycle was immediately initiated, with endometrial thickness measuring 4 mm. Eleven days after the second transfer, the beta hCG value was inappropriately high. A right tubal pregnancy corresponding to 8 gestational weeks was diagnosed. Laparoscopy revealed a prominent right tubal pregnancy in addition to a significantly smaller left tubal pregnancy. The discordant tubal pregnancies were confirmed histologically. To our knowledge, superfetation involving a second ectopic pregnancy coexistent with a first, contralateral ectopic pregnancy consequent to consecutive in vitro fertilization procedures has not previously been described in the medical literature. This case emphasizes the importance of routine beta hCG testing after every IVF cycle, even if apparently unsuccessful. This report describes a unique case of bilateral tubal superfetation in an anovulatory woman undergoing consecutive frozen thawed single-blastocyst transfers in separate artificial cycles.