title: High incidence of monozygotic twinning in infertility treatment.
abstract: BACKGROUND
  Monozygotic twinning is associated with increased perinatal morbidity and mortality. There is evidence that the number of monozygotic twins increases after assisted reproductive techniques.
  
  
  METHODS
  We searched PUBMED, MEDLINE, and Scopus from 1987 to 2015 for studies analyzing the incidence and possible etiology of monozygotic twinning in infertility patients and critically reviewed the current state of knowledge.
  
  
  CONCLUSIONS
  Monozygotic twinning is a rare in natural conception but occurs around twice the normal rate after assisted reproduction. Factors associated with this phenomenon remain speculative, though there is some evidence that micromanipulation techniques, prolonged culture, and genetics are involved. In view of the possible complications, adequate pre-conception counselling is advocated.
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital Olomouc and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic.|Fertimed Infertility Center, Boleslavova 2, 77200 Olomouc, Czech Republic.
authors.forename: Ales
authors.initials: A
authors.lastname: Sobek
authors.affiliation: Department of Medical Genetics, University Hospital Olomouc and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Prochazka
authors.affiliation: Fertimed Infertility Center, Boleslavova 2, 77200 Olomouc, Czech Republic.|Department of Paediatrics, University Hospital Olomouc and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Klaskova
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital Olomouc and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Lubusky
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital Olomouc and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic.
authors.forename: Radovan
authors.initials: R
authors.lastname: Pilka
mesh_terms: D000367:Age Factors; D005260:Female; D006801:Humans; D007246:Infertility / Q000628:therapy*; D011247:Pregnancy; D059285:Pregnancy, Twin / Q000502:physiology*; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*; D038522:Twinning, Monozygotic / Q000235:genetics / Q000502:physiology; D014430:Twins, Monozygotic
keywords: incidence; infertility; monozygotic twins; risk factors