After adjustment for all potential confounders such as genetics and maternal age, the use of antidepressants during the second or third trimester was associated with an 87 percent increased of autism, while no association was observed between the use of antidepressants during the first trimester or the year before pregnancy and the risk of autism.

The results indicated the increased risk of autism was observed with selective serotonin reuptake inhibitors and with the use of more than one class of antidepressant during the second and third trimester.

"It is biologically plausible that antidepressants are causing autism if used at the time of brain development in the womb, as serotonin is involved in numerous pre- and postnatal developmental processes, including cell division, the migration of neuros, cell differentiation and synaptogenesis -- the creation of links between brain cells," Berard explained.

"Some classes of anti-depressants work by inhibiting serotonin (SSRIs and some other antidepressant classes), which will have a negative impact on the ability of the brain to fully develop and adapt in-utero," she said.

The findings are hugely important as six to ten percent of pregnant women are currently being treated for depression with antidepressants and the World Health Organization indicated that depression will be the second leading cause of death by 2020, which led the researchers to believe that antidepressants will likely to remain widely prescribed, including during pregnancy.

"Our work contributes to a better understanding of the long-term neurodevelopmental effects of anti-depressants on children when they are used during gestation. Uncovering the outcomes of these drugs is a public health priority, given their widespread use," Berard added.