The association between maternal occupation and down syndrome: A report from the national Down syndrome project

Background: Among live births, Down syndrome (DS) due to trisomy 21 is the most commonly occurring autosomal trisomy, typically resulting from meiotic nondisjunction. Currently, advanced maternal age and altered recombination patterns are the only well-known risk factors for nondisjunction. Maternal occupation has not been investigated as a risk factor for maternally-derived cases of trisomy 21. Objectives: This study explored the association between maternal occupation and chromosome 21 nondisjunction, stratified by the stage of maternal error - either Meiosis I (MI) or Meiosis II (MII). Additionally, we investigated specific toxic agents associated with occupation classes. Methods: Using narrative job descriptions from the National Down Syndrome Project (NDSP), a population-based case-control study, occupation was coded using the 2010 Standard Occupational Classification (SOC). Odds ratios were calculated for the association between occupation class and having a child with DS, stratified by meiotic stage. An exposure analysis was performed within occupational classes that were statistically significant predictors of having a child with DS. Odds ratios were calculated to analyze associations between individual exposures and having a child with DS. Results: The odds of MII nondisjunction were increased among Production Workers (OR = 3.15; 95%CI = 1.52,6.55). Women who worked as Life, Physical and Social Scientists or in Food Preparation and Serving-Related Occupations experienced greater likelihood of MI errors (OR = 5.72(1.80,18.20), and OR = 1.87(1.08,3.24), respectively). Exposure to solvents within the Production Worker group was a significant predictor (p < 0.05) for MI nondisjunction. No other environmental agents had a significant association with nondisjunction. Discussion: Specific maternal occupation classes were associated with MI and MII chromosome 21 nondisjunction. These occupation classes were selected for an exposure analysis, which determined solvents as highly predictive of MI nondisjunction among Production Workers. Findings from this analysis will serve to further explore the relationship between maternal occupation and chromosome 21 nondisjunction.