title: The Relationship Between Offspring Sex Ratio and Vasectomy Utilization.
abstract: OBJECTIVE
  To determine if there was an association between vasectomy utilization and offspring sex ratio (male offspring : total offspring), as offspring sex preference may have an impact on family planning in the United States.
  
  
  METHODS
  Using data from the National Institutes of Health-AARP Diet and Health Study, we calculated the number of sons and daughters of all men stratified by vasectomy status. We utilized a logistic regression model to determine if vasectomy utilization varies based on offspring sex ratio while accounting for known factors that impact vasectomy utilization.
  
  
  RESULTS
  Of these men, 30,927 (30.8%) underwent vasectomy. Marital status, race, age, education level, region or state, and number of offspring were all significantly correlated with vasectomy utilization (P < .01). The sex ratio for vasectomized fathers (51.3%) was significantly higher than for fathers who had not undergone vasectomy (50.7%, P < .01). This difference remained even after we stratified by the total number of offspring: vasectomized men with 4 or more children had a sex ratio of 947 girls per 1000 boys, whereas the no vasectomy group had a sex ratio of 983 girls per 1000 boys (P < .01). For men with at least 2 children, each additional son increased the likelihood of vasectomy by 4% (P < .01), whereas each additional daughter led to a 2% decrease in vasectomy utilization (P = .03).
  
  
  CONCLUSIONS
  Vasectomized fathers have a higher proportion of sons compared with non-vasectomized fathers, suggesting that offspring sex ratio is associated with a man's decision to undergo vasectomy. Further research is indicated to understand how offspring sex ratio impacts a man's contraceptive decisions.
authors.affiliation: Department of Urology, Stanford University School of Medicine, Stanford, CA.
authors.forename: Remy W
authors.initials: RW
authors.lastname: Lamberts
authors.affiliation: Department of Urology, Stanford University School of Medicine, Stanford, CA.
authors.forename: David P
authors.initials: DP
authors.lastname: Guo
authors.affiliation: Department of Urology, Stanford University School of Medicine, Stanford, CA.
authors.forename: Shufeng
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Urology, Stanford University School of Medicine, Stanford, CA. Electronic address: eisenberg@stanford.edu.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Eisenberg
mesh_terms: D002755:Choice Behavior; D003657:Decision Making; D005220:Fathers; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D009679:Nuclear Family; D016017:Odds Ratio; D012044:Regression Analysis; D012744:Sex Ratio; D014481:United States; D014659:Vasectomy / Q000706:statistics & numerical data*