Abstract
<p>The predictive value of maternal age and maternal education in relation to rates of mild, moderate/severe, and profound mental retardation (MR) in a three-year birth cohort were studied. Epidemiological methodology was used to quantify both individual-level and population-level risk based on an electronically linked, statewide database of birth and school records (n = 267,277). Consistent with previous studies, both low maternal education and older maternal age were associated with increased risk for MR. Among mothers who did not finish high school, the lowest risk age group (25 to 29 years of age) was nearly 4 times (RR = 12.91) more likely to have a child with mild MR than the highest risk age group (40 to 44 years of age) among college-educated mothers (RR = 3.44). For moderate/severe MR, there was a sharp increase in risk over the age of 35 within all levels of maternal education, but the rate for mothers with less than 12 years of education was 3 times higher than that of college-educated mothers. In addition, when older, college-educated mothers had children with MR, they tended to have mild rather than moderate/severe school placements. Rates of profound MR showed little variation by maternal age or maternal education, In terms of population-level risk, it was the youngest mothers (15 to 24 years of age) with 12 years of education or less whose births were associated with the greatest risk for mild MR and moderate/severe MR in the population. Despite the well-known increased individual-level risk for moderate/severe MR accompanied by older maternal age, the relatively large number of births to women in the 15 to 24 age group was responsible for the increased population-level risk. The powerful association of maternal education with developmental outcomes, even in the face of significant biological risks such as older maternal age, makes low maternal education a key target for early intervention for both individuals and the population. In particular, early intervention programs may want to target mothers with <12 years of education in addition to biological risk factors.</p>