The Association Between Maternal Toxoplasmosis and Childhood Autism: A Scoping Review

Introduction: Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is a congenital infection capable of crossing the placenta during pregnancy, potentially disrupting fetal neurodevelopment. Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition with multifactorial origins, including possible environmental and infectious contributors. This scoping review aims to synthesize existing evidence on the association between maternal toxoplasmosis and the risk of ASD in offspring. Methods: This review followed the Arksey and O’Malley framework for scoping reviews, incorporating five methodological steps: (۱) identifying the research question, (۲) conducting a comprehensive literature search, (۳) selecting relevant studies, (۴) charting the data, and (۵) summarizing and reporting the findings. A systematic search was conducted across PubMed, ScienceDirect, and Google Scholar using keywords such as "maternal toxoplasmosis," "autism," "pregnancy infection," and "neurodevelopmental disorders." From an initial pool of ۲۵۰ articles, ۱۵ studies published between ۲۰۰۰ and ۲۰۲۳ met the inclusion criteria. Studies of lower methodological quality were included but categorized separately due to the exploratory nature of scoping reviews. Results: Among the ۱۵ studies analyzed, findings were grouped into three categories. Seven studies reported a positive association between maternal toxoplasmosis and ASD, suggesting mechanisms such as cytokine-induced neuroinflammation, oxidative DNA damage, and epigenetic alterations (e.g., abnormal DNA methylation) that may disrupt fetal brain development. These studies often adjusted for confounders like maternal age but varied in terms of the timing of infection assessment. Five studies found no significant association, potentially due to genetic heterogeneity, inconsistent serological markers (IgG/IgM), or lack of environmental adjustment. While these studies generally had larger sample sizes, they differed in diagnostic criteria and methodological rigor. Three studies yielded inconclusive results, citing limitations such as small sample sizes, reliance on self-reported infection status, and inconsistent ASD diagnostic standards. The heterogeneity across studies highlights the complex interplay of biological, environmental, and methodological variables, underscoring the need for standardized, large-scale investigations. Conclusion: Current evidence on the association between maternal toxoplasmosis and ASD remains equivocal, necessitating robust population-based, and mechanism-focused research. Enhanced prenatal screening and longitudinal studies are recommended to elucidate this potential risk factor.

Keywords:

maternal toxoplasmosis , autism , pregnancy infection , neurodevelopmental disorders