title: Conclusions about the effects on fertilization of time from aspiration to incubation and blood in the aspirate depend on the use of appropriate statistical techniques.
abstract: OBJECTIVE
  To examine the effects of exposure to blood and time from aspiration to incubation on oocyte fertilization.
  
  
  METHODS
  Retrospective, cohort study.
  
  
  METHODS
  Hospital-based IVF practice.
  
  
  METHODS
  Eighty-two women undergoing IVF procedures.
  
  
  METHODS
  Patients received a standard gonadotropin protocol or a microdose flare protocol.
  
  
  METHODS
  Logistic regression was used to estimate odds of nonfertilization, adjusting for maternal age, time from aspiration to incubation, presence of blood in the aspirate, and a time-by-blood interaction. Two statistical methods were used: an analysis that assumed oocytes were independent and an analysis that adjusted for the lack of independence of oocytes within mothers (i.e., cluster-correlated data).
  
  
  RESULTS
  The 82 women contributed 1093 oocytes. In a model with blood dicotomized as present or absent, and with time elapsed and maternal age categorized into quartiles, both time and maternal age were statistically significant when conventional logistic regression was used. In analyses that accounted for clustering within mother, retrieval-to-incubation times more than 4 minutes were associated with an increased risk of nonfertilization, but age and blood were not; there was no evidence of an interaction between time elapsed and blood.
  
  
  CONCLUSIONS
  If appropriate statistics are applied, retrieval-to-incubation times more than 4 minutes are associated with increased risk of nonfertilization.
authors.affiliation: Greenville Hospital System, Greenville, South Carolina 29605-5601, USA.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Crane
authors.forename: George W
authors.initials: GW
authors.lastname: Divine
authors.forename: Dawn W
authors.initials: DW
authors.lastname: Blackhurst
authors.forename: Carla L
authors.initials: CL
authors.lastname: Black
authors.forename: H Lee
authors.initials: HL
authors.lastname: Higdon
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Price
authors.forename: William R
authors.initials: WR
authors.lastname: Boone
mesh_terms: D000328:Adult; D001769:Blood; D015331:Cohort Studies; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D016015:Logistic Models; D009865:Oocytes; D012189:Retrospective Studies; D013396:Suction; D013997:Time Factors; D020858:Tissue and Organ Harvesting; D016896:Treatment Outcome