title: Very low birthweight: dysregulated gestation versus evolutionary adaptation.
abstract: Much medical literature attributes persistently high rates of very low birthweight (VLBW) to "dysregulated" gestation. We offer the alternative view that natural selection conserved well-regulated, though nonconscious, decisional biology that protects the reproductive fitness of women by spontaneously aborting gestations that would otherwise yield frail infants, particularly small males. Modern obstetric practice, however, converts some fraction of these erstwhile spontaneous abortions into live births of very small infants. We further propose that the nonconscious decisional biology of gestation exhibits preferences also seen in consciously made decisions. We hypothesize that the incidence of VLBW among male infants should vary with the population's self-reported intentions to assume financial risk. We apply time-series modeling to monthly birth counts by sex and weight from the Swedish Medical Birth Registry between January 1993 and December 2010. We gauge risk aversion with monthly data from the Micro Index of the Swedish Consumer Tendency Survey (MISCT). Consistent with our argument that nonconscious decisional biology shares risk aversion with conscious decisions, we find that the incidence of VLBW among male infants in Sweden varies with the population's self-reported intentions to assume financial risk. We find increases above expected odds of a very low weight infant among males born 1 month after increases above expected levels of self-reported risk aversion in the Swedish population. We offer this finding as support for the argument that persistently high rates of VLBW arise, at least in part, from a combination of medical interventions and mechanisms conserved by natural selection to protect reproductive fitness.
authors.affiliation: School of Public Health, 50 University Hall #7360, University of California, Berkeley, CA 94720, USA. Electronic address: rayc@berkeley.edu.
authors.forename: Ralph
authors.initials: R
authors.lastname: Catalano
authors.affiliation: School of Public Health, 50 University Hall #7360, University of California, Berkeley, CA 94720, USA. Electronic address: dkarasek@berkeley.edu.
authors.forename: Deborah
authors.initials: D
authors.lastname: Karasek
authors.affiliation: Department of Demography, 2232 Piedmont Ave., University of California, Berkeley, CA 94720, USA. Electronic address: alisong@demog.berkeley.edu.
authors.forename: Alison
authors.initials: A
authors.lastname: Gemmill
authors.affiliation: School of Public Health, 50 University Hall #7360, University of California, Berkeley, CA 94720, USA. Electronic address: April.falconi@berkeley.edu.
authors.forename: April
authors.initials: A
authors.lastname: Falconi
authors.affiliation: School of Public Health, 50 University Hall #7360, University of California, Berkeley, CA 94720, USA. Electronic address: juliagoodman@berkeley.edu.
authors.forename: Julia
authors.initials: J
authors.lastname: Goodman
authors.affiliation: School of Public Health, 50 University Hall #7360, University of California, Berkeley, CA 94720, USA. Electronic address: aristotlem@earthlink.net.
authors.forename: Aristotle
authors.initials: A
authors.lastname: Magganas
authors.affiliation: Institute for Housing and Urban Research, Uppsala University, Box 514, SE-75120 Uppsala, Sweden. Electronic address: terry.hartig@ibf.uu.se.
authors.forename: Terry
authors.initials: T
authors.lastname: Hartig
mesh_terms: D005075:Biological Evolution; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D008297:Male; D011247:Pregnancy / Q000502:physiology*; D012042:Registries; D018570:Risk Assessment; D013548:Sweden
keywords: Decision-making; Economy; Perinatal health; Risk aversion; Selection in utero; Sweden; Very low birthweight