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J Gend Specif Med. 2001;4(1):41-9.

Gender-related physiologic differences in human neonates and the greater vulnerability of males to developmental brain disorders.

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Center for Human Development Research, Department of Psychiatry and Behavioral Sciences, University of Texas-Houston Medical School, UT-MSI, 1300 Moursund St, Houston, TX 77030, USA.



To examine whether gender-specific physiologic differences are present at birth and can be a basis for gender-specific vulnerability to developmental disorders in males. We report on three studies of male-female physiologic and structural differences in neonates and their relevance to observed differences in the incidence of developmental disorders in males.


Study I: 56 neonates were examined for cardiac reactivity to the Moro reflex. Study II: 863 neonates' basic anthropometric data were examined to demonstrate gender-specific differences in body proportions as a possible basis for psychophysiologic differences. Study III: Developmental data on 1000 one- to 26-week-old infants were analyzed for gender-specific developmental differences in rhythmic patterns of sleeping and eating.


Study I: There were gender-related differences in heart rate reactivity (male > female). Study II: Male newborns had significantly larger head/chest proportions, suggesting that they may have a greater metabolic demand, related to brain size. Study III: Mothers reported that infant males' sleeping rhythm developed significantly later than females', and that they slept for shorter periods at night.


Gender-related vulnerability in brain development is proposed, based on physiologic differences during a specific early sensitive period in development. This hypothesis may help to explain the overrepresentation of males reported for most developmental disorders.

[Indexed for MEDLINE]

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