title: Blastocyst transfer and monozygotic twinning.
abstract: OBJECTIVE
  To report two cases of monozygotic twinning after IVF-blastocyst transfer.
  
  
  METHODS
  Case report.
  
  
  METHODS
  Private practice in an assisted reproductive technology clinic.
  
  
  METHODS
  Two women treated with IVF-ET at the blastocyst stage.
  
  
  METHODS
  Pituitary down-regulation with luteal leuprolide acetate, ovulation induction with gonadotropins, IVF, sequential culture, blastocyst transfer, and P for luteal support.
  
  
  METHODS
  Levels of hCG, pelvic ultrasound examination, amniocentesis, obstetric follow-up, and cesarean section.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Monozygotic multiple gestations may be increased in IVF blastocyst transfers. The potential obstetric complications of this type of pregnancy should be discussed with patients.
authors.affiliation: Clínica de Reproducción Asistida FIV-Madrid and Instituto de Bioquímica, CSIC, Madrid, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Peramo
authors.forename: E
authors.initials: E
authors.lastname: Ricciarelli
authors.forename: J M
authors.initials: JM
authors.lastname: Cuadros-Fernández
authors.forename: E
authors.initials: E
authors.lastname: Huguet
authors.forename: E R
authors.initials: ER
authors.lastname: Hernández
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D014430:Twins, Monozygotic