title: Systematic review of worldwide trends in assisted reproductive technology 2004-2013.
abstract: BACKGROUND
  Assisted Reproductive Technology (ART) has undergone considerable changes over the last decade, with consequences on ART outcomes in different regions of the world being unknown.
  
  
  METHODS
  We conducted a systematic review of published national and regional ART registry data to assess how changes in clinical practice between 2004 and 2013 have impacted outcomes in Australia and New Zealand, Canada, Continental Europe, the United Kingdom (U.K.), Japan, Latin America, and the United States (U.S.). The data reflect 7,079,145 total ART cycles utilizing both fresh and previously cryopreserved embryos from autologous oocytes that resulted in 1,454,724 live births. This review focused on the following measures: ART cycle volume, use of cryopreserved embryos, single embryo transfer (SET), live birth rates in fresh and frozen-thawed cycles, and perinatal outcomes in recent years.
  
  
  RESULTS
  SETs and utilization of frozen-thawed embryos increased worldwide over the study period. In 2012 SET utilization in all ART cycles was highest in Japan and Australia/New Zealand (82.6% and 76.3% respectively) and lowest in Latin America (16.0%). While gradual improvements in live birth rates were observed in most regions, some demonstrated declines. By 2012-2013, fresh cycle live birth rates were highest in the U.S. (29%) and lowest in Japan (5%). In Japan, the observed decline in fresh cycle live birth rate coincided with transition to minimal stimulation protocols, transfer of frozen-thawed rather than fresh embryos, and implementation of an SET policy. Similarly, implementation of an SET policy in parts of Canada was followed by a decline in fresh cycle live birth rate. Increasing live birth rates in frozen-thawed embryo cycles, seen all over the world, partially compensated for declines in fresh ART cycles. During 2012-2013 Australia/New Zealand and Japan reported the lowest multiple delivery rates of 5.6 and 4% respectively while the US had the highest of 27%. In recent years, preterm delivery rates in all regions ranged between 9.0 to 16.6% for singletons, 53.9 to 67.3% for twins, and 91.4 to 100% for triplets and higher order multiples. Inconsistencies in the way perinatal outcome data are presented by various registries, made comparison between regions difficult.
  
  
  CONCLUSIONS
  ART practices are characterized by outcome differences between regions. International consensus on the definition of ART success, which accounts for perinatal outcomes, may help to standardize worldwide ART practice and improve outcomes.
  
  
  BACKGROUND
  PROSPERO ( CRD42016033011 ).
authors.affiliation: The Center for Human Reproduction, 21 East 69th Street, New York, NY, 10021, USA. vkushnir@thechr.com.|Wake Forest School of Medicine, Winston-Salem, NC, USA. vkushnir@thechr.com.
authors.forename: Vitaly A
authors.initials: VA
authors.lastname: Kushnir
authors.affiliation: The Center for Human Reproduction, 21 East 69th Street, New York, NY, 10021, USA.|Foundation for Reproductive Medicine, New York, NY, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Barad
authors.affiliation: The Center for Human Reproduction, 21 East 69th Street, New York, NY, 10021, USA.|University of Kansas Medical Center, Kansas City, KS, USA.|The Rockefeller University, New York, NY, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Albertini
authors.affiliation: The Center for Human Reproduction, 21 East 69th Street, New York, NY, 10021, USA.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Darmon
authors.affiliation: The Center for Human Reproduction, 21 East 69th Street, New York, NY, 10021, USA.|Foundation for Reproductive Medicine, New York, NY, USA.|University of Vienna School of Medicine, Vienna, Austria.|The Rockefeller University, New York, NY, USA.
authors.forename: Norbert
authors.initials: N
authors.lastname: Gleicher
mesh_terms: D001315:Australia; D001723:Birth Rate; D002170:Canada; D005060:Europe; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007564:Japan; D007843:Latin America; D050498:Live Birth; D009520:New Zealand; D011247:Pregnancy; D027724:Reproductive Techniques, Assisted / Q000706:statistics & numerical data* / Q000639:trends*; D014481:United States
keywords: Assisted reproductive technology; Embryo cryopreservation; In vitro fertilization; Live birth rates; Single embryo transfer