title: Shared risk aversion in spontaneous and induced abortion.
abstract: OBJECTIVE
  Does the incidence of spontaneous abortion correlate positively over conception cohorts with the incidence of non-clinically indicated induced abortion as predicted by shared risk aversion?
  
  
  CONCLUSIONS
  We find that the number of spontaneous and non-clinically indicated induced abortions correlates in conception cohorts, suggesting that risk aversion affects both the conscious and non-conscious mechanisms that control parturition.
  
  
  BACKGROUND
  Much literature speculates that natural selection conserved risk aversion because the trait enhanced Darwinian fitness. Risk aversion, moreover, supposedly influences all decisions including those that individuals can and cannot report making. We argue that these circumstances, if real, would manifest in conscious and non-conscious decisions to invest in prospective offspring, and therefore affect incidence of induced and spontaneous abortion over time.
  
  
  METHODS
  Using data from Denmark, we test the hypothesis that monthly conception cohorts yielding unexpectedly many non-clinically indicated induced abortions also yield unexpectedly many spontaneous abortions. The 180 month test period (January 1995 through December 2009), yielded 1 351 800 gestations including 156 780 spontaneous as well as 233 280 induced abortions 9100 of which were clinically indicated.
  
  
  METHODS
  We use Box-Jenkins transfer functions to adjust the incidence of spontaneous and non-clinically indicated induced abortions for autocorrelation (including seasonality), cohort size, and fetal as well as gestational anomalies over the 180-month test period. We use cross-correlation to test our hypothesized association.
  
  
  RESULTS
  We find a positive association between spontaneous and non-clinically indicated induced abortions. This suggests, consistent with our theory, that mothers of conception cohorts that yielded more spontaneous abortions than expected opted more frequently than expected for non-clinically indicated induced abortion.
  
  
  CONCLUSIONS
  Limitations of our work include that even the world's best registration system will not capture all spontaneous abortions and that results may not generalize beyond Denmark.
  
  
  CONCLUSIONS
  Our findings imply that abortion, intentional or 'spontaneous,' follows from a woman's estimate, made consciously or otherwise, of the costs and benefits of extending gestation given characteristics of the prospective offspring, likely environmental circumstances at birth, and maternal resources.
  
  
  BACKGROUND
  The Robert Wood Johnson Health and Society Scholars Program funded the research described in this manuscript. None of the authors has any conflict of interest to declare.
authors.affiliation: School of Public Health, University of California, Berkeley, CA 94704, USA rayc@berkeley.edu.
authors.forename: Ralph
authors.initials: R
authors.lastname: Catalano
authors.affiliation: Public Health & Planning, Policy and Design, University of California, Irvine, CA 92697, USA.
authors.forename: Tim A
authors.initials: TA
authors.lastname: Bruckner
authors.affiliation: School of Public Health, University of California, Berkeley, CA 94704, USA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Karasek
authors.affiliation: Department of Psychiatry, School of Medicine, University of California, San Francisco, CA 94118, USA.
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Adler
authors.affiliation: Department of Social Medicine, University of Copenhagen, 1017 Copenhagen, Denmark.
authors.forename: Laust H
authors.initials: LH
authors.lastname: Mortensen
mesh_terms: D000028:Abortion, Induced / Q000706:statistics & numerical data*; D000022:Abortion, Spontaneous / Q000453:epidemiology*; D003657:Decision Making; D003718:Denmark; D005260:Female; D006801:Humans; D015994:Incidence; D011247:Pregnancy; D043762:Reproductive Behavior / Q000523:psychology*
keywords: abortion; environmental effects; epidemiology; pregnancy; pregnancy termination; risk aversion