Children exposed to complications shortly before or during birth, including birth asphyxia and preeclampsia, were 15% more likely to develop autism spectrum disorder (ASD) than were children not exposed to complications, new research indicates.
The relative risk varied depending on the timing of the exposure, according to the Kaiser Permanente study, published online January 31 in the American Journal of Perinatology.
Specifically, antepartum complications were associated with a 22% (hazard ratio [HR], 1.22; 95% confidence interval [CI], 1.10 - 1.36) relative increase in risk, whereas intrapartum complications were associated with a 10% (HR, 1.10; 95% CI, 1.04 - 1.17) increase in risk. Among children exposed to ante- and intrapartum complications, the relative risk increase was 44% (95% CI, 1.26 - 1.63).
Darios Getahun, MD, PhD, MPH, from the Kaiser Permanente Southern California Department of Research & Evaluation in Pasadena, and colleagues, examined electronic health records of a diverse group of 401,660 children born in Kaiser Permanente Southern California hospitals between 1991 and 2009. In that time, 6255 of the children were diagnosed with ASD and more than a third (37%) had experienced perinatal complications. Those not diagnosed with ASD became the control group.
The average age at first diagnosis of ASD was 6.2 years (standard deviation, 3.3). The median follow-up for children with and without exposure to complications surrounding birth was 4.9 years and 10.6 years, respectively.
To be included in the study, children had to be single births with a gestational age of 28 weeks through 42 weeks and born without congenital abnormalities.
The higher risks were evident "even after adjusting for factors such as gestational age at birth and a mother's age, race and education," Dr Getahun said in a press release. The researchers also adjusted for such factors as smoking status, psychosocial disorders during pregnancy, and whether and when the mother received prenatal care.
In addition to birth asphyxia and preeclampsia, the authors note that other complications linked with ASD included premature separation of the placenta from the uterus, breech or transverse presentation, fetal dystocia/abnormal size or position, and a prolapsed or exposed umbilical cord.
The outcome in this study was an ASD diagnosis in children ages 3 to 17 years based on criteria listed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision.
The cause of ASD remains unclear, but emerging evidence points to both genetic and environmental factors. The authors conclude that pregnancy complications may help identify children who may be at risk for ASD and who may benefit from screening and interventions to enhance their development.
The size and diversity of the Kaiser cohort is a strength of the study. Previous studies likely weren't powered to study the effect of fetal hypoxia on ASD, according to the authors. Previous studies also have not studied whether ASD risk differs by the child's race or ethnicity or gestational age at birth.
According to the latest Centers for Disease Control and Prevention data, 1 in 68 eight-year-old children meet diagnostic criteria for ASD.
The study is supported by Kaiser Permanente Direct Community Benefit Funds. The authors have disclosed no relevant financial relationships.
Am J Perinatol. Published online January 31, 2017. Abstract