85 This study estimated the prevalence to be 5% in adolescents who had a birth weight <2000 g in the US, which is significantly greater than the last national prevalence estimates. Most of these subjects were born preterm (96.7%); however, 32.3% were small for gestational age and the authors did not use multivariate analyses to simultaneously control for birth weight and gestational age. This methodological Inhibitors,research,lifescience,medical issue concerns most of the studies on perinatal and neonatal risk factors, which makes it difficult to interpret the results of these studies, since many of the events studied are likely to occur at the same time. Another limitation to the

interpretation of the results is that some studies have suggested that increased rates of birth and pregnancy complications are likely secondary to familial factors associated with autism.86 Socioeconomic status Although one study did not find any association between risk of Inhibitors,research,lifescience,medical autism and socioeconomic status87 including maternal education level, the latter may significantly influence the age of first single words.88 Moreover, as already mentioned, Inhibitors,research,lifescience,medical autism risk was found to be significantly increased for the offspring of mothers born abroad in a meta-analysis.81 This risk was further specified in a very recent

study89 showing that children of migrant parents are at an increased risk of autism with intellectual disability, especially when parents migrated to Sweden from regions with a low human development index, and a decreased risk of high-functioning autism. The risk for low-functioning autism peaked when migration occurred around the time of pregnancy. Different mechanisms can be proposed to explain these results, such as the high level of maternal Inhibitors,research,lifescience,medical stress or low immunity regarding common infections. Drugs and toxic exposure As previously mentioned, exposure to medication Inhibitors,research,lifescience,medical during pregnancy was found to increase autism risk in the most recent meta-analyses.81 Prenatal exposure to valproate is a recognized risk factor for ASD, especially in the first trimester of pregnancy. Children exposed in utero to valproate have

8-fold increased risk to have ASD.90 Interestingly, a downregulation of NLGN3 was observed in hippocampal subregions and the somatosensory cortex of mice prenatally exposed to valproate.91 Moreover, one ol the major concerns regarding medication exposure during pregnancy concerns the use of antidepressants, of since selective serotonin selleck chemical reuptake inhibitor medication during pregnancy increased from 1.5% in 1996 to 6.4% in 2004 and 6.2% in 2005.92 It was suggested that antidepressant exposure during pregnancy modestly increases the risk of ASD, especially in the first semester.93 Lastly, exposure in utero to an organophosphate insecticide, chlorpyrifos, was found to increase ASD risk and it was suggested that synthetic chemicals should be far more explored.