Condition at Birth and Mental Deficiency

The conditions at the delivery of a sample of mentally defective subjects were analyzed on the basis of data in their obstetric records. The sample consisted of all persons living in the Stockholm County on June 1, 1962, who were born at a hospital in Stockholm or in the Stockholm or Uppsala County during the years 1940 to 1955, inclusive, and who were or who had been in institutions for the mentally deficient. This gave 349 subjects (195 men and 154 women), 193 severely retarded (IQ < 52) and 156 mildly retarded (IQ 52-84). These were compared with 698 control subjects matched for date of birth, sex and maternity hospital. Both the mildly and severely defectives differed significantly from the control subjects in weight, length and head circumference at birth. This was true for the severely retarded regardless of length of gestation, though the differences were larger when born after unusually short gestation. The average length of gestation for both the mildly and severely defectives did not differ significantly from that for the control subjects, but both groups of defectives showed greater variability in this length than did the control subjects. The mean maternal age was higher for the severely retarded than for the control subjects, regardless of the length of gestation. The mildly defective did not differ from the control subjects in this respect. Premature birth, breech delivery and twin birth occurred significantly more often among both the severely and mildly defective subjects. But no significant difference emerged in rate of forceps delivery, cesarean section, prolonged labour, placenta previa, other abnormal presentations than by the breech, toxemia of pregnancy or coiling of the umbilical cord around the neck of the infant. The mentally defective did not differ from the control subjects in the number of abortions or stillbirths their mothers had had before they were born. Nor was there any difference in previous rate of livebirths. On the other hand, sibships of over three members were over-represented among the mildly retarded. Both the mildly and severely defective subjects were significantly more often illegitimate than their control subjects. The author concludes with a short discussion on the difficulty of judging the significance of different perinatal factors to mental deficiency.