title: Monochorionic quadramniotic and triamniotic pregnancies following single embryo transfers: two case reports and a review of the literature.
abstract: OBJECTIVE
  The purpose of this study is to report two cases of monozygotic quadruplet and triplet pregnancies following single embryo transfer (ET).
  
  
  METHODS
  A 29-year-old woman and a 34-year-old woman underwent ART treatment in two affiliated University based ART units. The first woman underwent ICSI with day 3 embryo biopsy for pre-implantation genetic diagnosis (PGD) followed by day 4 transfer, which resulted in a monochorionic quadramniotic (MCQA) quadruplet pregnancy. The second woman underwent conventional IVF with transfer of a single blastocyst, which resulted in a monochorionic triamniotic (MCTA) triplet pregnancy.
  
  
  RESULTS
  The first patient underwent successful selective foetal reduction at 16 + 3 and 17 + 4 weeks of gestation. Two healthy twin girls were delivered by elective caesarean section at 35 + 6 weeks of gestation. The second patient underwent successful selective foetal reduction at 14 + 1 weeks of gestation. The remaining monochorionic diamniotic (MCDA) twins are well at the time of writing this article.
  
  
  CONCLUSIONS
  To our knowledge, these cases represent the first case of viable MCQA pregnancy following single ET in the world and the third case of a viable MCTA pregnancy following conventional IVF with single ET. Several factors including blastocyst stage transfer and zona pellucida manipulation have been thought to contribute to monozygotic twinning in the context of ART. These two cases add to the growing literature of monozygotic multiple pregnancies following ART.
authors.affiliation: Assisted Reproductive Technology Unit, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Sotirios H
authors.initials: SH
authors.lastname: Saravelos
authors.affiliation: Center for Reproductive Medicine, Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200135, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Assisted Reproductive Technology Unit, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Jacqueline Pui Wah
authors.initials: JP
authors.lastname: Chung
authors.affiliation: Fetal Medicine Unit and Prenatal Diagnosis Center, Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: Lu-Ming
authors.initials: LM
authors.lastname: Sun
authors.affiliation: Center for Reproductive Medicine, Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200135, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Assisted Reproductive Technology Unit, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Tin-Chiu
authors.initials: TC
authors.lastname: Li
authors.affiliation: Center for Reproductive Medicine, Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200135, China. chenzijiang@hotmail.com.
authors.forename: Zi-Jiang
authors.initials: ZJ
authors.lastname: Chen
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D011247:Pregnancy; D059287:Pregnancy, Quadruplet; D059286:Pregnancy, Triplet; D019836:Preimplantation Diagnosis; D027724:Reproductive Techniques, Assisted; D056826:Single Embryo Transfer / Q000009:adverse effects / Q000379:methods*; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods; D038522:Twinning, Monozygotic / Q000502:physiology; D014430:Twins, Monozygotic; D016216:Ultrasonography, Prenatal
keywords: ICSI; IVF; Multiple pregnancy; Pre-implantation genetic diagnosis; Ultrasound