Stressful Life Events during Pregnancies Related to Children with ASD, Their Siblings and Typically Developing Children

Background:  The role of stressful events in contributing to increased autism risk deserves special attention since very few studies have attempted to collect this kind of information. Adverse experiences during the prenatal period (a time of rapid growth and of heightened brain plasticity) have been demonstrated to induce significant effects on neurobiology, metabolism, and physiology that can persist across the lifespan. Generally, the more variable the stressor and the earlier the stressors occur in the pregnancy, the more profound the effect on offspring development. A number of basic science studies indicate that a family history of stress may program central and peripheral pathways regulating gestational length and newborn health outcomes in the maternal lineage. Epigenomic programming related to hypothalamic-pituitary-adrenal (HPA) axis responses to chronic stress may be an important mechanism involved in autism development.

Objectives:  The aim of this study was to assess the frequency and impact of different stressful life events. Data was collected from careful interviewing during pregnancies of the following three groups: mothers of children with ASD, of their typically developing siblings (internal controls) and of only typically developing children ( external controls) in two Italian provinces, Como and Pisa.

Methods:  

The clinical sample included a cases group of 73 ASD children and adolescents – group 1 (mean age 8.2; S.D. 6.35) compared to  an internal control group formed by 45 healthy siblings – group 2 (mean age 8.9 years; S.D. 6.66) and to an external control group formed by 96 typically developing children – group 3 (mean age  7.8; S.D 5.67). It is important to note that the second  group represented all the siblings available. Mothers of ASD children who met the inclusion criteria were invited to an individual structured interview about stressful life events after having signed an informed consent form. Stressful events considered in the survey were: death or severe disease of a relative, divorce, separation or conjugal conflict, loss of house or eviction or relocation, abuse or violence and job strain.

Results:  

A statistically higher prevalence of the mean number of stressful events per pregnancy  was recorded  in  the ASD group when compared to the internal and external control groups. The mean number stressful events (range) was = 0.45(0-5 ), 0.29(0-3)  and 0.11(0-2 ) in the three groups respectively. Group 1 vs group 2: p< 0.05; Group 1 vs group 3: p <0.001; Group 2 vs group 3 p<0.01.

Conclusions:  Stressful life events during pregnancy are more frequent in mothers of children with autism than mothers of typically developing children. The rate observed in sibling pregnancies lies exactly in the middle, pointing out a possible threshold effect in women predisposed to suboptimal pregnancies.