Low Intelligence and Obstetric Complications

Investigations into the association between low intelligence and obstetric complications have been inconclusive.Dayton (1930) wrote that "the literature on mental deficiency is replete in its references to difficult labour as an aetiological factor in the production of intelligence defects".But in a retrospective inquiry he found no evidence that abnormal deliveries were associated more frequently with the births of subnormal children.Pasamanick and Lilienfeld (1955) looked at the birth records of subnormal children in Baltimore and concluded that "the pre-natal and paranatal records of mentally defective children born in Baltimore between 1935 and 1952 showed significantly more complications of pregnancy and delivery, prematurity, and abnormal neonatal conditions than a similar number of matched controls.The non-mechanical abnormalities such as bleeding during pregnancy and toxaemia appear to be important factors in this association rather than the mechanical factors of delivery previously described".Stott (1957) claimed that "'pregnancy troubles might be responsible for a large, and probably the greater part of the re- tardation" of the subnormal children whom he was studying.Rauramo, Gronross, and Kivikoski (1961) obtained the delivery reports of pupils in a school for backward children, and concluded that there was a raised incidence of forceps delivery, breech birth, toxaemia of pregnancy, and prolonged labour.It is difficult to assess the results of these studies because they are based on comparisons between unrepresentative samples of subnormal children and control groups which do not seem adequate.These methodological difficulties were largely overcome by