title: Delay of embryo transfer to day 5 results in decreased initial serum beta-human chorionic gonadotropin levels.
abstract: OBJECTIVE
  To investigate the impact of delaying the transfer of in vitro fertilized embryos to day 5 on embryo development by comparing serum beta-hCG levels in pregnancies established after day 3 embryo transfers and those after day 5 blastocyst transfers at equivalent time intervals after fertilization.
  
  
  METHODS
  A retrospective analysis.
  
  
  METHODS
  Assisted reproductive technology center in an academic research environment.
  
  
  METHODS
  Women who had an embryo transfer procedure performed after in vitro fertilization (IVF) at Northwestern University's IVF Program between January 1999 and December 2001 were included in this study.
  
  
  METHODS
  Embryo transfer was performed either on day 3 or day 5 after oocyte retrieval for IVF (day 0), depending on the availability of good-quality embryos on day 3.
  
  
  METHODS
  Serum beta-hCG concentrations determined 13 and 15 days after fertilization in pregnancies established by transferring cleavage-stage embryos on day 3 or blastocysts on day 5.
  
  
  RESULTS
  In singleton pregnancies, serum beta-hCG concentrations were 75 +/- 54 (mean +/- SD, n = 203) or 62 +/- 41 (n = 109) IU/mL after day 3 or day 5 transfers, respectively. In twin pregnancies, the beta-hCG concentrations were 162 +/- 105 (n = 52) or 109 +/- 55 (n = 49) after day 3 or day 5 transfers, respectively. The percentage increases in beta-hCG concentrations between the first and second measurements were similar in the two groups (day 3: 144 +/- 109, day 5: 142 +/- 63, not statistically significant).
  
  
  CONCLUSIONS
  Initial beta-hCG concentrations in pregnancies resulting from day 5 transfers were lower than those from day 3 transfers when assessed at equivalent intervals from fertilization. This suggests that embryo development or implantation may be impaired by the additional 2 days in culture.
authors.affiliation: Department of Obstetrics and Gynecology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA. zhang3@northwestern.edu
authors.forename: Xingqi
authors.initials: X
authors.lastname: Zhang
authors.forename: Randall
authors.initials: R
authors.lastname: Barnes
authors.forename: Edmond
authors.initials: E
authors.lastname: Confino
authors.forename: Magdy
authors.initials: M
authors.lastname: Milad
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Puscheck
authors.forename: Ralph R
authors.initials: RR
authors.lastname: Kazer
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004624:Embryo Transfer / Q000145:classification*; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D009865:Oocytes / Q000166:cytology*; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013997:Time Factors; D014310:Triplets; D014427:Twins
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human