The importance of obstetric complications in sporadic and familial psychoses was analyzed in 43 schizophrenic and 28 chronic schizoaffective patients. Patients and first-degree relatives were diagnosed using Research Diagnostic Criteria and the best-estimate procedure. Mothers of patients were interviewed for histories of pregnancy and obstetric complications in their offspring. Patients had more often suffered perinatal complications (42%) than their siblings (29%). The risk for obstetric complications and secondary cases of psychosis was enhanced in relatives of patients with a history of obstetric complications. Siblings with obstetric complications had a low incidence of psychoses; therefore, obstetric complications could not explain the occurrence of secondary cases of psychosis in siblings. Patients with familial psychoses had a higher incidence of obstetric complications than did sporadic cases (without reaching statistical significance). There was no inverse relationship between the history of obstetric complications in patients and the morbid risk of first-degree relatives for psychoses. The familial versus sporadic distinction revealed no subgroups where obstetric complications were of special relevance.
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