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 IVF-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, amniocentesis, 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 transfusion 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 blastocyst transfers. The potential obstetric complications of this type of pregnancy should be discussed with patients.