Schizophrenia is a psychiatric disease affecting around 1% of the population, the negative signs of which are correlated with inactivity of the prefrontal dorsolateral cortex, while an increased, more deeply localized, activity in the mesolimbic pathway may explain the positive signs. Several events occurring during pregnancy are likely to be involved in its genesis: hormonal supplementation by diethylstilbestrol, severe maternal denutrition, exposure to influenza virus, repeated psychological stress. From multicentric studies and meta-analyses in the psychiatric literature, the risk of schizophrenia appears to be multiplied by two if pregnancy is complicated, mainly by diabetes, Rhesus incompatibility, bleeding, preeclampsia, premature rupture of membranes and preterm birth. When delivery is linked to an abnormal presentation or happens via a caesarean birth for acute foetal distress, the time when the first signs of psychosis appear seems to be earlier in adolescence or in early adulthood. Cerebral imaging of schizophrenic patients shows ventriculomegaly and gray matter reduction, mainly in hippocampal volumes and in the dorsolateral prefrontal cortex. Similar alterations in the neuronal pathways have been experimentally reproduced in rats after repeated prenatal stress and perinatal hypoxia. A region on the distal portion of chromosome 1 has shown evidence for linkage to schizophrenia. Therefore, a two factor model seems to be able to explain the onset of schizophrenia in which obstetrical complications may interact with a genetic liability and in which the consequences of hypoxic events may lie on a continuum ranging from cerebral palsy in some children to subtle cognitive and behavioural disturbances in others.