The authors gathered and analyzed data on a population-based cohort of 96,736 children, all of them were born in Denmark from 1997 to 2003.
Their mothers were asked what illnesses, especially infections and fevers they had during their pregnancies and the early days after giving birth. They were also asked about any antibiotic use during those periods.
The following maternal infections were not linked to autism risk in their offspring:
- Respiratory infections
- Urinary tract infections
- Genital infections
- Sinus infections
- Influenza (flu) - pregnant mothers who caught the flu had twice the risk of giving birth to a baby who eventually was diagnosed with an autism spectrum disorder before the age of three years
- Fever - pregnant mothers who said they had a fever that lasted for at least one week had three times the risk of giving birth to a baby who eventually was diagnosed with an ASD before the age of 3
- Antibiotic usage - pregnant mothers who took antibiotics had a slightly higher risk of having a baby with an ASD
Lead researcher, Hjordis Osk Atladottir, MD, PhD, said that women who catch the flu or have a fever during pregnancy should not be alarmed by these findings. Approximately 98% of those who did catch flu or had a lasting fever gave birth to children with no ASD.
Recent research finding more links to autism riskOlder fathers - older father's have a higher risk of having children with some kind of ASD than younger fathers. Researchers explained in the journal Nature that an older father has a higher chance of passing on new mutations to his offspring than older mothers.
Specific gene mutations - scientists from the Seattle Children's Research Institute discovered new gene mutations which were associated with the development of autism, epilepsy, hydrocephalus and cancer. They were mutations in the following genes - AKT3, PIK3R2 and PIK3CA. Their study was published in Nature Genetics (July 2012 issue).
Immune system irregularities - researchers from Caltech (California Institute of Technology) reported in PNAS (Proceedings of the National Academy of Sciences) (July 2012 issue) that specific changes in an overactive immune system can contribute to autism-like behaviors in mice. They added that in some cases, this activation may be related to how a fetus develops while in the womb.
Parents with bipolar disorder or schizophrenia - a child whose parents or sibling have been diagnosed with bipolar disorder or schizophrenia has a higher risk of being diagnosed with an autism spectrum disorder, scientists from The University of North Carolina reported in Archives of General Psychiatry (July 2012 issue).