Prenatal risk factors for autism: comprehensive meta-analysis
S. L. Buka
The British Journal of Psychiatry,
2009, 195(1), 7-14. DOI: 10.1192/bjp.bp.108.051672
The aetiology of autism is unknown, although prenatal exposures have been
the focus of epidemiological research for over 40 years.
To provide the first quantitative review and meta-analysis of the
association between maternal pregnancy complications and pregnancy-related
factors and risk of autism.
PubMed, Embase and PsycINFO databases were searched for epidemiological
studies that examined the association between pregnancy-related factors and
autism. Forty studies were eligible for inclusion in the meta-analysis.
Summary effect estimates were calculated for factors examined in multiple
Over 50 prenatal factors have been examined. The factors associated with
autism risk in the meta-analysis were advanced parental age at birth, maternal
prenatal medication use, bleeding, gestational diabetes, being first born
v. third or later, and having a mother born abroad. The factors with
the strongest evidence against a role in autism risk included previous fetal
loss and maternal hypertension, proteinuria, pre-eclampsia and swelling.
There is insufficient evidence to implicate any one prenatal factor in
autism aetiology, although there is some evidence to suggest that exposure to
pregnancy complications may increase the risk.