Obstetric complications in individuals diagnosed with autism and in healthy controls

Abstract

The aim of the present study was to investigate birth complications in Israeli autistic probands. We interviewed 206 mothers of autistic probands and 152 healthy control mothers with a structured tool encompassing prenatal, perinatal, and neonatal complications. Analysis of obstetric suboptimality, derived by summing all positive items of each of the 3 categories and dividing them by the number of patients analyzed, revealed no prenatal between-group difference. The controls had a somewhat elevated perinatal suboptimality score, whereas the autistic probands had a significantly greater neonatal suboptimality score. These differences in obstetric suboptimality were retained after controlling for the demographic parameters found different between the 2 groups (sex of participants and mothers' years of schooling). Our findings suggest that the presence of nonspecific neonatal factors, rather than the specific influence of individual severe insults, may account for the elevated neonatal suboptimality found in probands diagnosed with autism compared with healthy controls.

Introduction

Genetic factors are known to contribute significantly to the etiology of autism [1]. Nevertheless, environmental noninherited factors, particularly physical damage to the central nervous system during pregnancy, may also be important in the development of autism [2]. Several studies have shown an elevated rate of birth complications in individuals with autism compared with control populations [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], although no single complication has yet emerged as a consistent risk factor for its development [5], [6], [7], [12]. The interrelationship between autism and obstetric complications may be confounded by the influence of birth order. That is, obstetric complications may be more frequent in firstborn children—in families with 2 children, or in late-born children—in families with at least 3 or 4 children [4], [5], [8], [12], although at least 1 study did not report such findings [6]. In addition, a significantly decreased obstetric optimality was retained in several studies in probands with autism after taking birth-order effect into account [5], [9].

Several models have been hypothesized to explain the relationship between obstetric complications and autism. Autism may represent a heterogeneous entity, where in some cases genetic factors, and in other cases environmental factors, may predispose to the disorder [2], [13]. Alternatively, birth complications associated with autism may represent an epiphenomenon of the autistic disorder, namely, stem from impairment in fetal development that decreases obstetric optimality or that a shared familial risk factor (or factors) may increase the risk for both autism and birth complications [3], [5], [7], [14]. A third model hypothesizes that an interaction may exist between genetic and environmental factors in the predisposition to autism, namely, that birth complications may increase the risk for autism in individuals who are genetically vulnerable to develop the disorder [7], [12] or if these individuals are part of a family with a predisposition toward cognitive disability [15].

The aim of the present study was to assess the prevalence of birth complications in patients diagnosed with autism and in a community control group. We hypothesized that autistic probands will show an elevated rate of a combination of mild nonspecific birth complications, rather than a few individual severe complications, compared with healthy controls.