Babies whose mothers had signs of active genital herpes infection during early pregnancy may be twice at risk for developing autism spectrum disorder (ASD) later, say researchers.
Genital herpes is a highly contagious virus and lifelong infection that usually spread through sex.
The research showed an association between maternal anti-herpes simplex virus-2 (HSV-2) antibodies and risk for autism in children.
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"We believe the mother's immune response to HSV-2 could be disrupting foetal central nervous system development, raising risk for autism," said lead author Milada Mahic, research scientist at Columbia University Mailman School of Public Health in New York City.
The risk of autism was found to be the result of primary or reactivation of infection in mothers with inflammation in close proximity to the womb, the researchers suggested.
"Evidence suggests a role for both genetic and environmental factors. Our work suggests that inflammation and immune activation may contribute to risk. Herpes simplex virus-2 could be one of any number of infectious agents involved," added W. Ian Lipkin, Director at Columbia University.
For the study, appearing in the journal mSphere, the team examined blood samples from 412 mothers of children diagnosed with autism and 463 mothers of children without autism.
Samples were taken at two time points at around week 18 of pregnancy and at birth and analysed for levels of antibodies five pathogens: Toxoplasma gondii, rubella virus, cytomegalovirus and herpes simplex viruses type 1 and 2 known as ToRCH agents, exposure to which can lead to miscarriage and birth defects.
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The risk was found with high levels of antibodies to HSV-2, not any of the other agents and was only evident in blood samples taken at a time point reflecting exposure during early pregnancy when the foetal nervous system undergoes rapid development, not at birth.