title: Timing of birth: Parsimony favors strategic over dysregulated parturition.
abstract: OBJECTIVE
  The "dysregulated parturition" narrative posits that the human stress response includes a cascade of hormones that "dysregulates" and accelerates parturition but provides questionable utility as a guide to understand or prevent preterm birth. We offer and test a "strategic parturition" narrative that not only predicts the excess preterm births that dysregulated parturition predicts but also makes testable, sex-specific predictions of the effect of stressful environments on the timing of birth among term pregnancies.
  
  
  METHODS
  We use interrupted time-series modeling of cohorts conceived over 101 months to test for lengthening of early term male gestations in stressed population. We use an event widely reported to have stressed Americans and to have increased the incidence of low birth weight and fetal death across the country-the terrorist attacks of September 2001. We tested the hypothesis that the odds of male infants conceived in December 2000 (i.e., at term in September 2001) being born early as opposed to full term fell below the value expected from those conceived in the 50 prior and 50 following months.
  
  
  RESULTS
  We found that term male gestations exposed to the terrorist attacks exhibited 4% lower likelihood of early, as opposed to full or late, term birth.
  
  
  CONCLUSIONS
  Strategic parturition explains observed data for which the dysregulated parturition narrative offers no prediction-the timing of birth among gestations stressed at term. Our narrative may help explain why findings from studies examining associations between population- and/or individual-level stressors and preterm birth are generally mixed.
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: Ralph
authors.initials: R
authors.lastname: Catalano
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: Julia
authors.initials: J
authors.lastname: Goodman
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: Claire
authors.initials: C
authors.lastname: Margerison-Zilko
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: April
authors.initials: A
authors.lastname: Falconi
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: Alison
authors.initials: A
authors.lastname: Gemmill
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: Deborah
authors.initials: D
authors.lastname: Karasek
authors.affiliation: School of Public Health, University of California, Berkeley, California, 94720.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Anderson
mesh_terms: D002140:California / Q000453:epidemiology; D015331:Cohort Studies; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D047928:Premature Birth / Q000453:epidemiology* / Q000209:etiology; D013312:Stress, Physiological; D023481:Terrorism; D013997:Time Factors