A new study from the University of Missouri, School of Medicine revealed that expecting mothers who have a stress-sensitive gene and were exposed to stress during pregnancy were most likely to give birth to a child with autism spectrum disorder.

Previous researches have already showed that environmental factors, such as stress, play an important role in the development of autism in children. However, there are some mothers who experience tremendous stress during pregnancy that gave birth to a normal child.

In order to understand why some mothers under significant amount of stress don't have children with autism while others do, researchers conducted a study involving a gene that is known to affect stress.

The study, published in the journal Autism Research, discovered a link between a variation of the stress-sensitive gene known as 5-HTTLPR and the development of autism with exposure to stress.

5-HTTLPR regulates the neurotransmitter serotonin in the nervous system. This gene when altered disrupts the availability of serotonin, causing an increase reaction to stress.

For the study, researchers studied two separate groups of mothers from MU Thompson Center for Autism and Neurodevelopmental Disorders and Queen's University in Ontario, Canada. Both groups of mother have a child with autism spectrum disorder. The mothers were surveyed about any possible stress they experienced during their pregnancies. These stresses may include, but not limited to, loss of a job, moving or divorce. The researchers also took blood samples from the mothers to test for a variation of 5-HTTLPR.

The researchers then discovered that mothers who have a variation of 5-HTTLRP experience more stress during the end of the second and the beginning of the third trimester of pregnancy, while mothers who do not carry the altered gene did not report experiencing more stress.

In a press release, researchers noted that the study is purely observational and does not provide any concrete proof to show causal relationship between the altered gene and autism. However, with their findings, there is a high chance in the future that health care providers can identify women who may be at a greater risk of having a child with autism when exposed to stress.