hDIiN.L 699and delivery in an ambulance-do result in impaired academic performance among children at ordinary schools, it seems unlikely that they exert more than a small influence on the intellectual development of children exposed to them. The distributions of scores of affected children were unimodal (Tables VI and XI) and therefore provided no evidence of a substantial group of children whose development was greatly impaired; and there were only small differences in the mean scores of affected and unaffected sibs. A previous analysis of the relation between obstetric complications and subnormal intelligence (an I.Q. below 75), based on the same obstetric data as the present analysis, revealed an association between educational subnormality and both precipitate labour and delivery in the absence of a qualified attendant (Barker, 1966). But neither of these complications seems to be associated with impaired performance within the normal range of intelligence.The mean V.R. scores of children delivered instrumentally or by caesarean section were higher than those of the population and of their unaffected sibs. It seems reasonable to suppose that a child born by caesarean section may avoid cerebral damage sustained in a normal delivery; but it is difficult to explain the association between instrumental delivery and raised V.R. scores. The data are, however, too complex to justify the conclusion that instrumental delivery will improve school performance.The finding that the mean V.R. score in the population declines with increasing birth rank (Table II) confirms numerous previous observations of the negative correlation between fraternity size and measured intelligence. But this inquiry has also shown that within fraternities there is an average fall of 1.0 in V.R. score with each unit increase in birth order.
SummayBirth records of 50,000 children were linked with records of school performance at the age of 11. Twins and triplets showed marked impairment, and were excluded from this study. The verbal reasoning (V.R.) scores of single-born children exposed to obstetric complications were compared with those of the population and of their sibs. The results suggested that impaired performance was associated with only five of the obstetric complications studied: a short gestation period, a prolonged gestation period, toxaemia, occipito-posterior presentation, and delivery in an ambulance. In no case was the impairment very marked. Within fraternities there was a fall in average V.R. score with increasing birth rank.
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