title: Trends and factors associated with the Day 5 embryo transfer, assisted reproductive technology surveillance, USA, 2001-2009.
abstract: OBJECTIVE
  What characteristics are associated with a Day 5 embryo transfer?
  
  
  CONCLUSIONS
  The use of the Day 5 embryo transfer has increased over time, with clinicians allowing women with typically 'poorer' prognostic characteristics to undergo a Day 5 embryo transfer. The mean number of embryos per Day 5 transfer decreased from 2001 to 2009, although the prevalence of the Day 5 single embryo transfer remains low and the rate of multiple births remains substantial.
  
  
  BACKGROUND
  Day 5 embryo transfer may reduce the rate of multiple gestation pregnancy. US trends over time in the prevalence of the Day 5 transfer, changes in characteristics of patients receiving Day 5 transfer, and number of embryos transferred are unknown.
  
  
  METHODS
  We used 2001-2009 US National assisted reproductive technology (ART) Surveillance System (NASS) data on 620,295 fresh IVF cycles derived from autologous oocytes with a Day 3 or 5 embryo transfer. Trends in the mean number of embryos transferred from 2001 to 2009 were assessed by the day of transfer. For 349,947 cycles from clinics performing both Days 3 and 5 embryo transfers, multivariable logistic regression was used to determine the characteristics associated with the Day 5 embryo transfer. We also compared the characteristics of the Day 5 embryo cycles in 2001 and 2009.
  
  
  RESULTS
  Overall, the proportion of ART cycles using the Day 5 embryo transfer increased from 12% in 2001 to 36% in 2009 (P<0.0001), while the mean number of embryos transferred decreased from 2.4 to 2.1 (P<0.0001). Among Day 5 transfers, the rate of the single embryo transfer tripled from 4.5% in 2001 to 14.8% in 2009 (P<0.0001); and the rate of multiple births decreased from 44.8 to 41.1% (P<0.0001). In cycles initiated after 2001, maternal age<35 years, no prior ART cycles, ≥1 prior pregnancies, baseline follicle stimulating hormone<10 international units and ≥10 oocytes retrieved were associated with the Day 5 embryo transfer. Compared with 2001, in 2009, a broader range of candidates received the Day 5 transfer. BIAS Women undergoing multiple ART cycles over time are not linked.
  We ran multivariable logistic regression to lessen the effects of the confounding factors. Cycle cancelation rates by the day of embryo transfer are unknown.
  
  
  CONCLUSIONS
  Generalizable to ART clinics included in NASS.
  
  
  BACKGROUND
  This study was funded by the Centres for Disease Control. The authors have no competing interests to declare.
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan Health System, 1500 E. Medical Center Drive, L4510 Women's Hospital, Ann Arbor, MI 48109, USA. rowlanda@med.umich.edu
authors.forename: Courtney A
authors.initials: CA
authors.lastname: Marsh
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Farr
authors.forename: Jeani
authors.initials: J
authors.lastname: Chang
authors.forename: Dmitry M
authors.initials: DM
authors.lastname: Kissin
authors.forename: David A
authors.initials: DA
authors.lastname: Grainger
authors.forename: Samuel F
authors.initials: SF
authors.lastname: Posner
authors.forename: Maurizio
authors.initials: M
authors.lastname: Macaluso
authors.forename: Denise J
authors.initials: DJ
authors.lastname: Jamieson
mesh_terms: D000328:Adult; D001723:Birth Rate; D001755:Blastocyst / Q000166:cytology; D004624:Embryo Transfer / Q000379:methods / Q000639:trends*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000639:trends; D006801:Humans; D007246:Infertility / Q000628:therapy; D008297:Male; D011247:Pregnancy; D027724:Reproductive Techniques, Assisted / Q000639:trends*; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States