Monozygotic twinning is a relatively rare event in vivo conception, being estimated to occur in 0.42% of all birth. The underlying mechanism for monozygotic twin formation is the division of the embryo early in its development. Separation of cells may theoretically occur before or after inner cell mass formation. The incidence of monozygotic twinning following assisted reproduction techniques is higher than the commonly accepted incidence after in vivo conception. Patients at particular risk of monozygotic twins are those aged > 35 years and those who had manipulation techniques for assisted fertilization. Hence, it seems prudent to counsel these patients about the potential obstetric complications of monozygotic multiple gestations prior to the initiation of their treatment.
Embryonic Structures ; Fertilization ; Fertilization in Vitro* ; Humans ; Incidence ; Parturition ; Reproductive Techniques ; Twinning, Monozygotic ; Twins, Monozygotic*

OBJECTIVE: To report three cases of monozygotic twinning after IVF-ET transfer. METHODS: Private practice in two different assisted reproductive technology clinics. RESULTS: Three intrauterine monozygotic twin pregnancies occurred after IVF-ET. One of them was complicated by cord entanglement, another is progressing normal pregnancy without complication and the other was had a normal pregnancy without complication and delivered twin by cesarean section. CONCLUSION: The reported prevalence of multiple gestations in IVF-ET is a approximately 30%, and it is only 2.7% to be monozygotic twinning in IVF-ET. We report three cases of monozygotic twining after IVF-ET.
Cesarean Section ; Female ; Humans ; Pregnancy* ; Prevalence ; Private Practice ; Reproductive Techniques, Assisted ; Twinning, Monozygotic ; Twins, Monozygotic*

One of the most important complications in assisted reproductive technology (ART) is multiple pregnancy, which is associated with an increased risk of maternal and perinatal complications. There have been several attempts to achieve the highest pregnancy rates while minimizing multiple pregnancy rates in in vitro fertilization and embryo transfer (IVF-ET). One approach for this purpose is extended embryo culture and transfer of fewer (one or two) blastocysts. However, there are emerging concerns about the increase of the risk for embryo splitting and subsequent monozygotic multiple pregnancy with this approach. Recently, there have been several reports on the possible increased risk of monozygotic twinning after extended embryo culture and blastocyst transfer. We have experienced a case of two sets of monozygotic twins after intracytoplasmic sperm injection (ICSI) and transfer of two blastocysts. We report the first case of pregnancy of monozygotic twins after blastocysts transfer with a brief review of literature in Korea.
Blastocyst* ; Embryo Transfer* ; Embryonic Structures ; Female ; Fertilization in Vitro ; Humans ; Korea ; Pregnancy ; Pregnancy Rate ; Pregnancy, Multiple ; Reproductive Techniques, Assisted ; Sperm Injections, Intracytoplasmic* ; Twinning, Monozygotic ; Twins, Monozygotic*