Prenatal exposure to heavy metals and the trajectory of autistic traits in childhood

Abstract

Background The association between prenatal heavy-metal exposure and autistic traits remains underexplored. Objectives This study aims to investigate the association between prenatal heavy-metal exposure and autistic traits in offspring, and their trajectories during childhood. Methods In a prospective birth cohort of 540 mother–child pairs, we measured maternal blood levels of lead, cadmium, mercury, and manganese during the second trimester. Autistic traits were assessed at ages 4, 6, 8, and 10 years, and trajectories were identified using latent class growth modeling. Regression models examined associations between individual and mixture effects of prenatal heavy-metal exposure and autistic traits at each age, as well as their trajectories (low vs. high score classes). Results Prenatal lead exposure was significantly associated with autistic traits at 8 years (15.8 % increase per doubling; 95 % confidence interval [CI], 2.1–31.4). In girls, prenatal lead exposure was associated with autistic traits at 6 (46.4 % increase; 95 % CI, 19.0–80.1), 8 (57.9 % increase; 95 % CI, 26.0–98.0), and 10 (32.3 % increase; 95 % CI, 5.8–65.4) years. Prenatal lead exposure was associated with trajectory class only in girls, with an odds ratio (OR) of 2.7 (95 % CI, 1.0–6.9) for belonging to the high-score class per doubling of exposure. Maternal heavy-metal mixtures were marginally associated with autistic trait trajectories. Conclusion This is the first study to link prenatal heavy-metal exposure with autistic trait trajectories. Prenatal lead exposure showed consistent associations across multiple childhood stages in girls, highlighting the need to reduce prenatal exposure and to consider sex-specific developmental pathways in neurodevelopmental research.