title: A prospective, randomized study: day 3 versus hatching blastocyst stage.
abstract: BACKGROUND
  Recently, advances in human IVF-embryo transfer (ET) have been reported using sequential media and blastocyst stage ET. In our previous report, using a prospective, randomized study, no advantage was found using the blastocyst stage ET compared with day 3 ET. This study was performed in order to evaluate implantation and pregnancy rates of hatching blastocyst stage ET compared with conventional day 3 ET.
  
  
  RESULTS
  A total of 480 patient cycles were evaluated using a prospective, randomized study. The pregnancy rate and implantation rate were compared between the day 3 ET (n = 240) and hatching blastocyst stage ET (Hat ET; n = 240). The Hat ET group had a pregnancy rate of 29.3% (55 out of 188) and an implantation rate of 21.4% (67 out of 313). The day 3 ET group had a pregnancy rate of 29.2% (70 out of 240) and an implantation rate of 19.1% (93 out of 488). In the Hat ET group, the pregnancy rate, implantation rate and ongoing pregnancy rate of day 5 ET and day 6 ET were all higher than the respective rates in the day 7-9 ET group.
  
  
  CONCLUSIONS
  We found that the pregnancy rate and implantation rate of ET with hatching stage blastocysts had no advantage compared with the conventional day 3 ET.
authors.affiliation: St Luke Clinic, 5, Tsumori-Tomioka, Oita City 870-0947, Japan. st-luke@oct-net.ne.jp
authors.forename: Takafumi
authors.initials: T
authors.lastname: Utsunomiya
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ito
authors.forename: Miyuki
authors.initials: M
authors.lastname: Nagaki
authors.forename: Junko
authors.initials: J
authors.lastname: Sato
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies