title: A prospective, randomized study of embryo transfer results after 3 or 5 days of embryo culture in in vitro fertilization.
abstract: OBJECTIVE
  To compare the implantation rate of embryos after 3 and 5 days of IVF culture.
  
  
  METHODS
  Prospective randomization of ET depending on the weekday of ovum pick-up (OPU).
  
  
  METHODS
  University Department of Endocrinology and Reproduction.
  
  
  METHODS
  All women entering an outclinic IVF program.
  
  
  METHODS
  Two hundred thirty-three ETs performed on day 3 after OPU and 410 performed on day 5 were analyzed. When blastocysts with a clear inner cell mass were available, a maximum of two were replaced.
  
  
  RESULTS
  On day 3 after OPU, 60 pregnancies per 233 ET (26%) and on day 5, 102 pregnancies per 410 ET (25%) were induced. The average implantation rate per embryo was 13% and 12%, respectively. After subdivision according to embryo morphology, pregnancy rate per ET (n = 59) and implantation rate per embryo on day 3 with exclusively unfragmented embryos were 32% and 18%, respectively, not significantly different from ET (n = 73) exclusively with embryos containing > 0% and < 20% fragments: 27% and 12%. After transfer on day 5, when one or more cavitating embryos were available (n = 227), pregnancy and implantation rates were 40% and 23%, statistically different from ET on day 3. On day 5, ET exclusively with morula stages showing signs of starting blastulation (n = 26), pregnancy rate and implantation rate were 12% and 11%, respectively, from ET (n = 157) with embryos not reaching the latter stage: 6% and 3%.
  
  
  CONCLUSIONS
  Overall ET results after 3 and 5 days are comparable. After 5 days of culture, one to two embryos can be replaced with an average implantation rate of > 23% per embryo, minimizing the incidence of triplets.
authors.affiliation: Department of Endocrinology and Reproduction, Erasmus University, Rotterdam, The Netherlands.
authors.forename: M C
authors.initials: MC
authors.lastname: Scholtes
authors.forename: G H
authors.initials: GH
authors.lastname: Zeilmaker
mesh_terms: D001755:Blastocyst / Q000502:physiology; D046508:Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D011446:Prospective Studies; D013997:Time Factors