title: Effectiveness of 2-step (consecutive) embryo transfer. Comparison with cleavage-stage transfer.
abstract: OBJECTIVE
  To evaluate the effectiveness of 2-step (consecutive) embryo transfer (ET), in which two cleaved embryos are transferred on day 2 (first step of ET) and a single blastocyst is transferred on day 5 (second step of ET) in comparison with conventional day 2 ET.
  
  
  METHODS
  Observational comparative study at different time periods. Subjects were those who had > or = 4 embryos on day 2 after oocyte retrieval. Those in the conventional group (n = 60) received conventional day 2 ET, in which 3 cleaved embryos were transferred on day 2 between January 1999 and June 2000. Those in the 2-step group (n = 124) received 2-step embryo transfer, in which 2 cleaved embryos were transferred on day 2 and a blastocyst was transferred on day 5 between September 2000 and February 2002. Patients who planned to receive 2-step ET but could not proceed to the second step of ET because of failure to produce blastocysts were included in the 2-step group.
  
  
  RESULTS
  The ongoing pregnancy rate with 2-step ET (51.6%) was significantly higher than with conventional ET (26.7%) (P < .01). The clinical pregnancy rate and implantation rate in conventional and 2-step ET were 30.0% vs. 59.7% and 11.1% vs. 27.8%, respectively (P < .001).
  
  
  CONCLUSIONS
  Two-step ET may benefit patients who can obtain a sufficient number of embryos.
authors.affiliation: Department of Obstetrics and Gynecology, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu, Japan 520-2192.
authors.forename: Sakae
authors.initials: S
authors.lastname: Goto
authors.forename: Koichi
authors.initials: K
authors.lastname: Takebayashi
authors.forename: Masahide
authors.initials: M
authors.lastname: Shiotani
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Masaya
authors.initials: M
authors.lastname: Hirose
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Noda
mesh_terms: D000328:Adult; D001755:Blastocyst; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D013997:Time Factors