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Birth weight and two possible types of maternal effects on male sexual orientation: A clinical study of children and adolescents referred to a Gender Identity Service
Author(s) -
VanderLaan Doug P.,
Blanchard Ray,
Wood Hayley,
Garzon Luisa C.,
Zucker Kenneth J.
Publication year - 2015
Publication title -
developmental psychobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 93
eISSN - 1098-2302
pISSN - 0012-1630
DOI - 10.1002/dev.21254
Subject(s) - firstborn , sexual orientation , psychology , birth order , developmental psychology , birth weight , gender identity , demography , pregnancy , clinical psychology , social psychology , population , sociology , biology , genetics
This study tested predictions regarding two hypothesized maternal immune responses influencing sexual orientation: one affecting homosexual males with high fraternal birth order and another affecting firstborn homosexual individuals whose mothers experience repeated miscarriage after the birth of the first child. Low birth weight was treated as a marker of possible exposure to a maternal immune response during gestation. Birth weight was examined relative to sibship characteristics in a clinical sample of youth ( N = 1,722) classified as heterosexual or homosexual based on self‐reported or probable sexual orientation. No female sexual orientation differences in birth weight were found. Homosexual, compared to heterosexual, males showed lower birth weight if they had one or more older brothers—and especially two or more older brothers—or if they were an only‐child. These findings support the existence of two maternal immune responses influencing male sexual orientation and possibly also cross‐gender behavior and identity. © 2014 Wiley Periodicals, Inc . Dev Psychobiol 57: 25–34, 2015.