A new study has found a link between an infection in the womb and autism - especially in boys.
Experts have said the link is not caused as a result of direct infection, as these are often deadly. Researchers have suggested it could be triggered by the mother’s immune response to getting an infection causing neurodevelopmental problems.
It was linked with inflammation in close proximity to the womb when the unborn child is most vulnerable.
Norwegian and US scientists said there was a link between maternal anti-herpes simplex virus-2 (HSV-2) antibodies and risk for autism spectrum disorder in their child.
Dr Milada Mahic at the Norwegian Institute of Public Health, post-doctoral research scientist, said: "We believe the mother's immune response to HSV-2 could be disrupting foetal central nervous system development, raising risk for autism."
Genital herpes is a common incurable sexually transmitted infection caused by the herpes simplex virus (HSV) leading to painful blisters.
It is highly contagious and a long-term condition with the virus remaining the body living in nerve cells.
However the body can build up immunity to the virus.
Until now the NHS said the risk of the virus to the unborn child in early pregnancy was low and women infected or experiencing a flare up are prescribed antiviral medicine.
The study explored the link between maternal infection and risk for autism, focusing on five pathogens - types of bacteria known collectively as ToRCH agents - which the herpes simplex virus.
Blood samples were taken from 412 mothers of children diagnosed with autism and 463 mothers of children without autism enrolled in the Autism Birth Cohort (ABC) Study overseen by the Norwegian Institute of Public Health.
Samples were taken at around week 18 of pregnancy and at birth and analysed for levels of antibodies to each of the bacteria.
They found high levels of antibodies to HSV-2, not any of the other agents, correlated with risk for Autism.
Experts said the link was only found in blood samples taken during early pregnancy.
It found an eighth - 13 per cent of mothers in the study tested positive for anti-HSV-2 antibodies at mid-pregnancy.
Of these, only 12 per cent reported having HSV lesions before pregnancy or during the first trimester.
The scientists said the effect of anti-HSV-2 antibodies on risk for autism was only seen in boys not girls.
But they noted the number of girls with autism in the study was small.
Professor Dr Ian Lipkin of the Centre for Infection and Immunity at Colombia University said: "The cause or causes of most cases of autism are unknown.
"But 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."
The study was published in mSphere, a journal of the American Society for Microbiology.
Link to original article: http://www.express.co.uk/life-style/health/771045/autism-test-sex-herpes-virus