Constitutional and genealogical factors
Medical history of ionizing radiation
Legal (alcohol and tobacco) and illegal drug use
Home remedy/herbal supplement use
Time of critical exposure: 20 to 24 days after conception
Time of critical exposure: first trimester, near sixth week after conception. Used for illegal abortion.
Time of critical exposure: first 3 to 4 weeks after conception. Neural tube defects, cardiac malformations, craniofacial malformation.
Time of critical exposure: infection during the first 8 weeks
Pesticide used at home, school, community and farms
Dicofol and endosulfan exposure. First to eighth weeks. Correlation between maternal residence near agricultural pesticide exposure and autism.
Prenatal, neonatal and perinatal factors
Advanced maternal and/or paternal age (mother > 35; father > 40); bleeding during pregnancy; forceps or vacuum delivery; prolonged labor; low birth weight (< 2500 g); respiratory distress syndrome; meconium aspiration syndrome; preterm birth at < 33 weeks; breech presentation; gestational age < 35 weeks; mothers who used medicine during pregnancy
Maternal immigration/mother born abroad
Increased risk of ASD according to region and ethnicity; more risk in Caribbean and African-American populations
Daily smoking in early pregnancy
The risk of autism is associated with daily smoking in early pregnancy
β2-Adrenergic receptor agonist
Used to treat premature labor. Continuous terbutaline exposure for 2 weeks had increased risk for ASD.
Associated with a near twofold increased risk for autism overall
Chlorinated solvents and heavy metals
Association between autism and estimated concentrations in ambient air around birth residence. Increased risk for solvent and metals (mercury, cadmium, nickel, trichloroethylene and vinyl chloride).
Parental psychiatric history
Parental psychopathology is associated with risk of autism and effective disorders
Alcohol and drugs
It is very unlikely that there is a strong association between prenatal alcohol exposure and autism
High parental education
Families with higher education background will seek services, thus reporting a child with autism
Lack of omega 3 fatty acids
Studies showed link between childhood development disorders and omega-6, omega-3 imbalances
Congenital cytomegalovirus (CMV) infection
Timing of injury to the developing brain by CMV may be in the third trimester in some patients with ASD
Singleton and concordant multiple births
Results indicated that ASD-concordant multiple births in boys tended to be higher than expected in March, May and September, but were 87% less in December, as compared with January
Maternal autoimmune disorders
Maternal autoimmune disorders in women around the time of pregnancy are unlikely to contribute significantly to risk of autism (case-control study)
Fetal alcohol syndrome (FAS) (case report)
Autistic behavior has not been previously associated with FAS. No statistical data, however it raises awareness that FAS could be a risk factor that should be evaluated by physicians.
Not a risk factor associated with ASD. Children with any degree of bilirubin level elevation were not at increased risk of ASD.
Antenatal ultrasound is unlikely to increase the risk of ASD (case-control study)
No reports of risk found
No risk found
Measles, mumps, rubella (MMR) vaccination
No evidence that supports MMR vaccination relationship with autism