There is little consensus as to which, if any, specific pregnancy and perinatal factors may be related to the development of adult schizophrenia, although accumulating evidence supports links with exposure to perinatal infection, poor nutrition and hypoxia. The evidence for a perinatal schizophrenia link is less secure than that for a childhood neurologic handicap.
Jones and associates conducted an investigation to determine the effect of pregnancy and neonatal factors associated with adult-onset schizophrenia in the delivered infant.
For each of the mothers of 11,017 infants in the 1966 North Finland birth cohort, standardized assessments made during pregnancy, delivery and the neonatal period were linked to the national psychiatric case register. Patients were followed until age 28. Seventy-six individuals who met the DSM-III-R criteria for schizophrenia were identified, as were links between perinatal events and subsequent development of schizophrenia.
Body mass indexes of the mothers were studied. The mothers with a body mass index of 29 or greater were more likely to have affected offspring, but this difference was not statistically significant. Smoking status was not predictive of schizophrenia. Women who described themselves as having been depressed during the sixth or seventh month of pregnancy were more likely to deliver an affected offspring. Factors such as maternal fever and abnormal delivery did not predict schizophrenia. The children with schizophrenia were more likely to have been born small and early, and evidence indicated that a small placenta was more common in this group. A short gestation period but an appropriate growth rate was associated with the development of schizophrenia in a subgroup of children. Subsequent schizophrenia was approximately seven times more likely in infants who had perinatal brain damage. Of the 125 survivors of severe perinatal brain damage, six (4.8 percent) eventually developed schizophrenia. Infants who spent a prolonged period of newborn life in the intensive care unit were also significantly more likely to develop schizophrenia.
The authors conclude that specific aspects of pregnancy and the perinatal period are associated with later development of schizophrenia and that these effects appear to be largely related to the child and not to the delivery per se. There was no association with conventional obstetric risk factors in the mothers. The possibility that schizophrenia may be more common in the large number of babies who survive significantly preterm birth remains a concern. The significance of timing is not completely clear, but the evidence indicates that very early birth may be a risk factor.