title: Extended embryo culture reduces the implantation rate on day 4 and day 5 when only a maximum of three embryos are cultured beyond the pronuclear stage.
abstract: OBJECTIVE
  To study the potential of embryo transfer after 3, 4 or 5 days of embryo culture under the German embryo protection law according to which only a maximum of three zygotes are allowed to be cultured for embryo transfer.
  
  
  METHODS
  In a prospective study, 273 patients with assisted reproductive treatment were randomly allocated for transfer on days 3, 4 or 5. Pregnancy and implantation rates were evaluated in regard to day of transfer and results were compared by Chi-square or ANOVA test.
  
  
  RESULTS
  Out of 234 transfer cycles, 79 were performed on day 3, 76 on day 4 and 79 on day 5. Pregnancy and implantation rates were 41.8%/27.1% for transfer on day 3, 27.6%/14.1% for day 4 transfer and 16.5%/8.8% for transfer on day 5. These results were significantly different for pregnancy rates on day 3 versus day 5 (P < 0.001) and for implantation rates on day 3 versus day 4 (P < 0.005) and day 3 versus day 5 (P < 0.001).
  
  
  CONCLUSIONS
  These findings suggest that extended embryo culture is not beneficial when the option for embryo selection at later stages of development is not available.
authors.affiliation: Department of Gynecological Endocrinology and Reproductive Medicine, University Clinics Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. Markus.Montag@ukb.uni-bonn.de
authors.forename: Markus
authors.initials: M
authors.lastname: Montag
authors.forename: Katrin
authors.initials: K
authors.lastname: van der Ven
authors.forename: Christoph
authors.initials: C
authors.lastname: Dorn
authors.forename: Hans
authors.initials: H
authors.lastname: van der Ven
mesh_terms: D000328:Adult; D046508:Culture Techniques; D010064:Embryo Implantation / Q000502:physiology*; D004624:Embryo Transfer; D005260:Female; D005858:Germany; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D027724:Reproductive Techniques, Assisted / Q000331:legislation & jurisprudence; D013997:Time Factors; D017388:Zygote Intrafallopian Transfer