Intellectual disability: Population-based estimates of the proportion attributable to maternal alcohol use disorder during pregnancy

Aim: The aim of this study was to examine the association between maternal alcohol use disorder and intellectual disability in children.

Method: All mothers with an International Classification of Diseases (ICD) 9 and/or 10 alcohol-related diagnosis, a proxy for alcohol use disorder, recorded on the Western Australian health, mental health, and drug and alcohol data sets were identified through the Western Australian Data Linkage Unit (n=5614 non-Aboriginal; n=2912 Aboriginal). A comparison cohort of mothers without an alcohol-related diagnosis was frequency matched on maternal age within maternal Aboriginal status and year of birth of their children. Linkage with the Western Australian Midwives Notification System (1983-2001) identified all births to these mothers (n=10664 and 7907 respectively). Linkage to the Western Australian Intellectual Disability Database and Register of Developmental Anomalies identified cases of intellectual disability with no identified genetic origin (intellectual disability) (n=1487) and fetal alcohol syndrome (n=66). Odds ratios (ORs) and 95% confidence intervals (CIs) for intellectual disability were calculated using logistic regression incorporating generalized estimating equations and used to estimate population-attributable fractions.

Results: At least 3.8% (95% CI 2.84-4.89%) of cases of intellectual disability could be avoided by preventing maternal alcohol use disorder: 1.3% (95% CI 0.81-1.86%) in non-Aboriginal and 15.6% (95% CI 10.85-20.94%) in Aboriginal children. We observed a three-fold increase in the adjusted odds of intellectual disability in children of mothers with an alcohol-related diagnosis recorded during pregnancy (non-Aboriginal OR 2.89, 95% CI 1.62-5.18; Aboriginal OR 3.12, 95% CI 2.13-4.56), with a net excess proportion of 3.7% and 5.5% respectively. One-third (32%) of children diagnosed with fetal alcohol syndrome had intellectual disability.

Interpretation: Maternal alcohol use disorder is the leading known risk factor for intellectual disability with no identified genetic origin.