RESUMEN
The frequency of twins resulting from a single embryo transfer has been reported to be 1.56%, with the majority being monochorionic. We present a case of septal rupture at 8 weeks of gestation and successful delivery at 36 weeks of gestation of a monozygotic dichorionic diamniotic twin after a single blastocyst transfer. This report could partially clarify the pathogenesis of monozygotic twins and septal disruption. A 37-year-old woman with 9 months of primary infertility was referred to our department. After seven cycles of artificial insemination, she underwent her first in vitro fertilization. Ten cumulous-oocyte complexes were retrieved, of which three were fertilized, and three blastocysts were cryopreserved. The first single blastocyst transfer in a hormone replacement cycle resulted in a dichorionic diamniotic twin pregnancy. Transvaginal ultrasound at 7 weeks and 4 days gestation revealed a size difference in the gestational sacs and a disruption of the inter-amniotic membrane between the two gestational sacs at 8 weeks and 6 days. Both fetuses were seen in the larger gestational sac; however, the umbilical cord of the migrated fetus was from the original gestational sac. Both fetuses developed without discordancy or obvious anomalies. At 36 weeks and 6 days of gestation, the patient underwent cesarean delivery, resulting in the birth of two viable male infants without any congenital anomalies (weighing 2256 g and 2456 g). Two amniotic cavities existed; however, no chorionic villi were present. There have been many reports on septal disruption in monochorionic diamniotic twins; however, only two cases of dichorionic diamniotic twins have been reported. Furthermore, the onsets in both reports were after the second trimester of pregnancy. This report presents the first case of septal disruption in dichorionic diamniotic twins during the first trimester.