Evidence that history of obstetric complications (OCs) may contribute to the development of schizophrenia has generated renewed focus on characteristics of mothers of preschizophrenics. We studied the relationship between increased history of obstetric complications (OCs) and maternal age, parity, and social class in 70 Research Diagnosis Criteria schizophrenic patients vs 70 demographically matched controls. The sample has previously been studied concerning OC rates in schizophrenic patients, their relationship to other presumptive etiological factors, as well as head circumference at birth. Parity was the only maternal characteristic significantly associated with increased OCs in mothers of preschizophrenics. As compared with nulliparous control mothers, nulliparous mothers of preschizophrenics had significantly increased rates of total OCs and labour/delivery complications, while primi- and multiparous mothers of preschizophrenics (vs parity-matched control mothers) did not have increased rates of OCs. Abnormal labour length was significantly increased in the nulliparous mothers of preschizophrenics. Previous findings of significantly reduced head circumference at birth in preschizophrenic neonates vs controls were reconfirmed selectively in the nulliparous group.