Etiological implication of maternal age and birth order in infantile autism

Abstract

Birth orders and maternal ages of the 113 autistic patients were compared with those of the general population. An excess of mothers aged 35 or older was observed in the autistic group, though the mean maternal age for the whole group was very similar to those of the general population. A deviation from average in birth order was observed in autistics. Significantly more autistics were products of at-risk pregnancies (defined as either first, fourth, or later born, or born to mothers aged 30 or older) than the base population. The results suggest that at least some environmental factors are involved in the causation of autism. The findings support the idea that a multifactorial mechanism is responsible for some or all of the cases.

Pre- and perinatal factors in high-functioning females and males with autism

“…A few factors (e.g., first or midtrimester bleeding, advanced maternal age, use of medications) have been found in more than one study (Campbell, Hardesty, & Burdock, 1978;DeMyer, 1979;Finegan & Quarrington, 1979;Gillberg & Gillberg, 1983;Torrey, Hersh, & McCabe, 1975;Tsai & Stewart, 1983). In general, however, only higher total scores on indices of complications and lower scores on indices of optimal pregnancies than normal control groups have been replicated consistently.…”

“…In addition, in line with the general association of autism and mental retardation, autistic samples have tended to be composed of many severely retarded youngsters, with fewer than 20% of the autistic subjects scoring above the range of mental retardation in previous studies. Even for the two studies in the last 10 years with the largest samples (Deykin & MacMahon, 1980;Tsai & Stewart, 1983), each with about 115 subjects, only about 25 subjects scored in the borderline to normal range of intelligence. Since previous research suggests that females may account for a greater proportion of lower functioning autistic samples than higher functioning samples, sex differences (or a lack of sex differences) may have been associated with differences in the proportion of subjects with severe mental retardation (Lord & Schopler, 1987).…”

“…The data presented here represent one part of an international collaborative study on sex differences in autism (Lord, Goode, Rutter, & Schopler, 1989). Because autistic females may be proportionately more severely mentally retarded than males (Lord & Schopler, 1985;Lord, Schopler, & Revecki, 1982;Tsai & Stewart, 1983), and because of our interest in factors specific to autism rather than those determined by mental retardation, the focus is on relatively high-functioning persons with autism. Altogether, the contribution of the current paper is the presentation of data from a relatively large sample of females, as well as from a relatively large sample of high-functioning persons with autism.…”

Advanced Parental Age and the Risk of Autism Spectrum Disorder

“…The possibility that autism is more common in offspring of older parents has generated considerable interest (1)(2)(3)(4)(5)(6). Confirmation of such an association could have important public health implications in light of increasing trends in recent decades regarding both maternal and paternal age (7).…”

“…Birth order is a potentially confounding factor because it is positively associated with parental age and has been reported in some studies to be associated with autism risk, with at least 3 studies reporting firstborn children to be at increased risk of autism (1,2,4). The goal of this study was to determine, in a large, population-based cohort of US children, whether advancing maternal and paternal age each independently increase a child's risk of developing autism after controlling for the other parent's age, birth order, and other risk factors.…”