title: Pregnancy outcomes of day 5 embryo transfer in patients at high risk of developing ovarian hyperstimulation syndrome and analysis of factors affecting blastocyst formation.
abstract: OBJECTIVE
  To investigate the effects of day 5 embryo transfer (D5ET) compared with day 3 embryo transfer (D3ET) in patients at high risk of developing ovarian hyperstimulation syndrome (OHSS); to analyse factors affecting blastocyst formation.
  
  
  METHODS
  Patients at high risk of developing OHSS underwent either D3ET or D5ET.
  
  
  RESULTS
  A total of 253 patients received D3ET; 263 received D5ET. The number of embryos transferred was lower in the D5ET group than in the D3ET group. There were no between-group differences in pregnancy or live birth rates. Implantation rate was higher, and multifetation rate lower, in the D5ET group compared with the D3ET group. In addition, the incidence of moderate or severe OHSS was lower in the D5ET group than in the D3ET group. The woman's age, gonadotrophin dosage and insemination method were associated with the quality of blastocyst formation.
  
  
  CONCLUSIONS
  In patients with a high risk of developing OHSS, compared with D3ET, D5ET decreased the multifetation rate and the incidence of moderate or severe OHSS, but did not affect the pregnancy or live birth rate. Women of a younger age, who have had an appropriate gonadotrophin dose and insemination by in vitro fertilization, are suitable candidates for blastocyst transfer.
authors.affiliation: Reproductive Medical Centre, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
authors.forename: Zhi-min
authors.initials: ZM
authors.lastname: Xin
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.forename: Hai-xia
authors.initials: HX
authors.lastname: Jin
authors.forename: Wen-yan
authors.initials: WY
authors.lastname: Song
authors.forename: Ying-pu
authors.initials: YP
authors.lastname: Sun
mesh_terms: D000328:Adult; D000367:Age Factors; D001755:Blastocyst / Q000000981:diagnostic imaging / Q000502:physiology*; D054796:Drug Dosage Calculations; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro; D006062:Gonadotropins / Q000627:therapeutic use*; D006801:Humans; D007247:Infertility, Female / Q000000981:diagnostic imaging / Q000628:therapy*; D050498:Live Birth; D016471:Ovarian Hyperstimulation Syndrome / Q000517:prevention & control*; D011247:Pregnancy; D012306:Risk; D012720:Severity of Illness Index; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D006062:Gonadotropins
keywords: Ovarian hyperstimulation syndrome; blastocyst culture; day 5 embryo transfer; pregnancy outcomes