title: Influence of parental and biological factors on the male birth fraction in the United States: an analysis of birth certificate data from 1964 through 1988.
abstract: OBJECTIVE
  To determine the role of parental and biological factors on the U.S. male birth fraction from 1964 through 1988.
  
  
  METHODS
  Logistic regression on annual U.S. male births by race group.
  
  
  METHODS
  Population-based data.
  
  
  METHODS
  Live births in the United States 1964 through 1988.
  
  
  METHODS
  None.
  
  
  METHODS
  Annual U.S. male birth fraction by parental and biological factors.
  
  
  RESULTS
  During the study period, the annual U. S. male birth fraction showed changes based on race group, parental age, and low birth weight. The overall influence of parental age on the U.S. male birth fraction is strong and is stronger in nonwhites than in whites. The U.S. male birth fraction is also strongly influenced by the percentage of low birth weight infants in nonwhites, but not in whites. The male birth fraction declines with increasing age of either parent and with an increase in the percentage of low birth weight infants.
  
  
  CONCLUSIONS
  The relative magnitude of influences on the U.S. male birth fraction depend on the race group, which may be a reflection of the range of observed data rather than biological differences. The developed models have reasonable predictive power and are an appropriate first step in understanding the factors influencing the male birth fraction. These types of parental and biological variables should be included in models before examining other exogenous and population level variables.
authors.affiliation: Epidemiology Section, Occupational Health Division, Exxon Biomedical Sciences, Inc., Annandale, New Jersey 08801-0971, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Nicolich
authors.forename: W W
authors.initials: WW
authors.lastname: Huebner
authors.forename: A R
authors.initials: AR
authors.lastname: Schnatter
mesh_terms: D000367:Age Factors; D001719:Birth Certificates; D001723:Birth Rate / Q000208:ethnology; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D010290:Parents; D011237:Predictive Value of Tests; D044469:Racial Groups; D012744:Sex Ratio; D014481:United States / Q000453:epidemiology; D044465:White People