title: Gay Male Only-Children: Evidence for Low Birth Weight and High Maternal Miscarriage Rates.
abstract: Recent findings suggest that there may be a maternal immune response underpinning the etiology of sexual orientation of gay male only-children. This maternal immune response appears to be distinct from that which is purported to explain the classic fraternal birth order effect found in studies of male sexual orientation. We tested two predictions related to the hypothesized maternal immune response in mothers of gay male only-children: (1) elevated fetal loss among mothers who have had gay male only-children and (2) lower birth weight in gay male only-children. Mothers of at least one gay son (n = 54) and mothers of heterosexual son(s) (n = 72) self-reported their pregnancy histories, including the birth weights of newborns and number of fetal losses (e.g., miscarriages). Mothers of gay male only-children (n = 8) reported significantly greater fetal loss compared with mothers of males with four other sibship compositions (gay with no older brothers, gay with older brothers, heterosexual only-children, heterosexual with siblings) (n = 118). Also, firstborn gay male only-children (n = 4) had a significantly lower birth weight than firstborn children in the four other sibship compositions (n = 59). Duration of pregnancy was not significantly different among the groups of firstborn children in the birth weight analyses. Thus, this study found further support for a distinct pattern of maternal immune response implicated in the etiology of male sexual orientation. Mechanisms that may underlie this potential second type of maternal immune response are discussed.
authors.affiliation: Department of Psychology, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada.
authors.forename: Malvina N
authors.initials: MN
authors.lastname: Skorska
authors.affiliation: Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON, M5T 1R8, Canada.
authors.forename: Ray
authors.initials: R
authors.lastname: Blanchard
authors.affiliation: Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road N., Mississauga, ON, L5L 1C6, Canada.|Child, Youth and Family Division, Underserved Populations Research Program, Centre for Addiction and Mental Health, Toronto, ON, Canada.
authors.forename: Doug P
authors.initials: DP
authors.lastname: VanderLaan
authors.affiliation: Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON, M5T 1R8, Canada.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Zucker
authors.affiliation: Department of Psychology, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada. tbogaert@brocku.ca.|Department of Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada. tbogaert@brocku.ca.
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Bogaert
mesh_terms: D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D018451:Homosexuality, Male / Q000706:statistics & numerical data*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009035:Mothers / Q000706:statistics & numerical data*; D009863:Only Child / Q000706:statistics & numerical data*; D011247:Pregnancy; D017584:Reproductive History
keywords: Birth order; Birth weight; Fetal loss; Maternal immune hypothesis; Miscarriage; Sexual orientation