Blastocyst transfer and monozygotic twinning

Objective: To report two cases of monozygotic twinning after IVF-blastocyst transfer. Design: Case report. Setting: Private practice in an assisted reproductive technology clinic. Patient(s): Two women treated with NF-ET at the blastocyst stage. Intervention(s): Pituitary down-regulation with luteal leuprolide acetate, ovulation induction with gonadotropins, IVF, sequential culture, blastocyst transfer, and P for luteal support. Main Outcome Measure(s): Levels of hCG, pelvic ultrasound examination, amni ocentesis, obstetric follow- up, and cesarean section. Result(s): Two intrauterine monozygotic twin pregnancies occurred after IVF and blastocyst transfer. One of them was complicated by fetus-to-fetus tra nsfusion syndrome and was delivered preterm by cesarean section; the other woman had a normal pregnancy and vaginal delivery. Conclusion(s): Monozygotic multiple gestations may be increased in IVF blas tocyst transfers. The potential obstetric complications of this type of pre gnancy should be discussed with patients. (Fertil Steril(R) 1999;72: 1116-7 . (C) 1999 by American Society for Reproductive Medicine).