The actual causes of ASD (Autism Spectrum Disorder) are still unknown, but certain factors are there that may increase the risk of ASD. There are some evidences that the critical period for developing ASD occurs before, during & immediately after birth. Some of the risk factors are as follow:-

• Genetic Factors – If a child have a brother, sister, twin or parents with ASD, than that child is more likely to have ASD. These include disorders such as Fragile X syndrome which causes intellectual disability and tuberous sclerosis which causes benign tumours to grow in the brain and other vital organs. Or other chromosomal disorders.
• Environmental Factors – Some experts suspect that exposure to heavy metals & other toxins in the environment increase the risk of ASD. Taking some drugs like valproic acid, paracetamol, thalidomide or misoprostol during pregnancy may double the risk of having a child with autism.
• A study founded that children born to iron deficient mothers are 5 times more likely to have Autism.
• 13% of Autism cases arises due to complications in pregnancy like- premature delivery, low birth weight or cesarean delivery but researchers emphasize that their finding do not indicate the cause of autism.
• A low prenatal level of vitamin D has been suggested to play an important role in risk of autism.