Can the mother’s workplace before and during pregnancy affect the child’s neural development? A large Danish study links several occupational categories, including transportation and defense jobs, to higher chances of an autism diagnosis in children, raising new questions about exposure to toxins, stress and prenatal health.
Study: Association between maternal occupational history and autism spectrum disorder diagnosis in offspring in Denmark.. Image Credit: Veja/Shutterstock.com
a fresh Occupational and Environmental Medicine Study examines relationship between maternal occupations and higher chances of autism spectrum disorder Diagnosis in offspring.
Maternal occupational exposure and autism: current evidence and research gaps.
Autism spectrum disorder (ASD) is a chronic neurodevelopmental disorder characterized by impairments in social communication and the presence of restricted or repetitive behaviors. The prevalence of ASD shows considerable global variability, with higher rates observed in males. In Denmark, the prevalence of ASD increased substantially between 2004 and 2015. Both genetic and environmental factors are believed to be involved in ASD etiology, with maternal exposures during pregnancy recognized as major influences on neurodevelopment.
Prenatal maternal occupational exposure to toxic chemicals is associated with abnormal neurodevelopment in offspring, including increased ASD odds related to exhaust, disinfectants, and organic solvents. Nevertheless, evidence regarding individual occupational exposures remains inconsistent, as some studies have found no association with cleaning products, metals, solvents, or pesticides. Occupational settings often involve concurrent exposure to multiple toxins and physical stressors.
Previous studies generally examined a narrow range of occupational categories and relied on self-report or birth record data, restricting assessment of exposure timing during key developmental periods. Detailed analysis of maternal employment history and exposure time in relation to ASD diagnosis is necessary, especially for occupations with variable chemical exposures.
Assessing the impact of maternal workplace on autism diagnosis.
The present study used Danish registry data to assess whether maternal occupation before and during pregnancy and infancy is associated with the odds of ASD diagnosis in children born in Denmark between 1973 and 2012.
Mothers were identified from the medical birth register and linked to Danish Pension Fund occupation data. Children were excluded if either parent was under 18 or over 66 at the time of birth, or if data were missing. A total analytic sample of 110,234 participants, including 1,702 ASD cases and 108,532 controls, was included.
The pension fund’s detailed job history allowed maternal occupations to be classified into 42 categories, coded as always/never held. Job exposures were assessed at multiple time points: up to 6 months before conception, 1 year before conception, during pregnancy, and during infancy.
Occupations were divided into seven sectors: service, transportation, freight/manufacturing, manufacturing, public service, business/finance/hospitality, and science, technology, engineering, and mathematics (STEM). Analyzes adjusted for child sex, birth year, mother’s age, parity, neuropsychiatric history, and residential location, with secondary adjustment for maternal smoking, marital status, immigration, and socioeconomic status.
The authors noted that occupational categories were used as a broad proxy rather than a direct measure of toxicant exposure and did not provide detailed information on specific work tasks, measured chemical exposures, or psychosocial stress levels. Furthermore, maternity leave records could not fully determine whether mothers were physically present at work during all exposure windows.
Increased ASD chances associated with specific maternal occupations
The study cohort was predominantly male, consisting of 71% of ASD cases and 70% of controls, most of whom were born in the 1990s. The average maternal age at the time of child’s birth was 29.3 years. Mothers of children with ASD more often than not control children have a history of neuropsychiatric disorders.
Within the goods and production sectors, maternal employment in chemical processing increased ASD odds in exploratory analyses, although the association varied by exposure period and did not remain consistently significant in exposure window and sensitivity analyses. The initial inverse relationship for agriculture and manufacturing, as well as the positive relationship for paper, printing, manufacturing, textiles, and clothing, remained no longer significant after statistical adjustment.
In public administration, increased ASD odds were most pronounced in female offspring, although this gender-specific association was attenuated after correction for multiple comparisons. Maternal employment in judicial roles was also associated with higher ASD odds, particularly during pregnancy. The overall pregnancy-window association for judicial occupations remained significant after statistical correction, although male-specific associations did not.
Higher odds were also seen in judicial and military/defense occupations before and during pregnancy. Initial findings for postal, telephone, and cleaning services, including the increased likelihood of female offspring for cleaning services, were not statistically significant after adjustment for multiple comparisons.
After statistical correction, no significant association was observed between maternal employment and outcomes in social well-being. However, defense occupations have consistently increased ASD odds in both male and potential female offspring. Maternal employment in science, technology, health, and most occupational fields showed no significant association with ASD diagnosis.
Overall, maternal employment in ground transportation (AOR 1.24), public administration (AOR 1.20), and military/defense (AOR 1.59) from conception to infancy was associated with increased ASD odds. These associations were particularly significant among male offspring for ground transportation and defense employment. However, some transportation-related findings were weakened after additional socio-demographic adjustments.
The study authors also discussed the possibility that both occupational toxins and psychosocial stress may contribute to neurodevelopmental outcomes through mechanisms involving inflammation, hormonal dysregulation, oxidative stress, and altered placental or fetal nervous system function, although these mechanisms were not directly measured in the study.
conclusion
The present study highlights the relationship between specific maternal occupations and increased ASD odds in offspring, with evidence of gender-specific effects. Because the study was observational, the findings do not establish causation. The findings emphasize the importance of considering occupational exposures before conception as potentially associated factors in neurodevelopmental outcomes.
The authors also noted that some occupational associations became weaker after multiple comparisons or adjustment for additional sociodemographic factors. Further research should focus on specific occupational exposures, underlying mechanisms, and phenotypic severity to better understand and mitigate these risks.
