Low intelligence. Its relation to length of gestation and rate of foetal growth.

More information is required about three aspects of the relation of low intelligence to birthweight and length of gestation:(I) Low birthweight is known to be associated with mental subnormality, but the significance of this remains unknown.(2) High birthweight has been reported to occur more frequently in association with subnormality, but the evidence is inconclusive.(3) Prolonged gestation has been suggested as a cause of cerebral damage and consequent intellectual impairment, but no data bearing on this issue appear to have been published.In this paper some observations which are relevant to these problems will be described. METHODSThe observations were made on a group of 606 subnormal children for whose low intelligence there is no known cause.These children were drawn from a population of 73,687 single births for whom obstetric data were recorded at the time of birth. POPULATION DATAThe population did not include children from multiple births but it otherwise comprised all children who were born in Birmingham during the years 1950-54 and who remained in the city until the age of 5 years.Obstetric data have been recorded for all births in Birmingham since 1950 (Charles, 1951) and recently these data have been transferred to magnetic tape to enable their analysis by computer.Birthweight was recorded, to the nearest quarter pound, for all but 68 of the births, and for 61,998 (84 per cent.) of the children the gestation period was known, calculated to the nearest week from the first day of the last menstrual period.No adjustments