title: Impact of monozygotic twinning on multiple births resulting from in vitro fertilization in the United States, 2006-2010.
abstract: OBJECTIVE
  To determine the contribution of monozygotic twining to in vitro fertilization multiple births.
  
  
  METHODS
  We performed a retrospective analysis of the incidence of monozygotic twining in multiple births resulting from fresh embryo transfers using 2006-2010 data from the Society for Reproductive Technology Clinic Outcome Reporting System.
  
  
  RESULTS
  The number of embryos transferred were fewer than the number of births in 0.5% (223/40950) of twin, 29% (659/2289) of triplet, and 64% (43/67) of quadruplet births resulting from transfer of fresh embryos from 2006 to 2010. In 2010, 37% of triplets and 100% of quadruplet births occurred when fewer than 3 and fewer than 4 embryos respectively were transferred.
  
  
  CONCLUSIONS
  Monozygotic twinning plays a key role in the development of triplet and quadruplet pregnancies achieved through in vitro fertilization.
authors.affiliation: Louisiana State University Department of Obstetrics and Gynecology, and School of Public Health, New Orleans, LA; Louisiana State University School of Medicine, and School of Public Health, New Orleans, LA.
authors.forename: Rebekah E
authors.initials: RE
authors.lastname: Gee
authors.affiliation: Louisiana State University Department of Obstetrics and Gynecology, and School of Public Health, New Orleans, LA; The Fertility Institute of New Orleans, Mandeville, LA.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Dickey
authors.affiliation: Tulane University Louisiana Department of Epidemiology, School of Public Health and Tropical Medicine, New Orleans, LA.
authors.forename: Xu
authors.initials: X
authors.lastname: Xiong
authors.affiliation: Louisiana State University Department of Obstetrics and Gynecology, and School of Public Health, New Orleans, LA.
authors.forename: Latoya S
authors.initials: LS
authors.lastname: Clark
authors.affiliation: Tulane University Department of Obstetrics and Gynecology, School of Medicine, New Orleans, LA.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Pridjian
mesh_terms: D004624:Embryo Transfer / Q000706:statistics & numerical data / Q000639:trends; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D011783:Quadruplets; D012189:Retrospective Studies; D056826:Single Embryo Transfer; D014310:Triplets; D014430:Twins, Monozygotic; D014481:United States
keywords: IVF; monozygotic twining; quadruplet birth; singleton birth; triplet birth; twin birth