Decreased birth weight in psychosis: Influence of prenatal exposure to serologically determined influenza and hypoxia

Background: Decreased birth weight (BW) is associated with later psychosis, but the sources of decreased BW for those at risk for psychosis remain unclear. Aim: To determine whether fetal exposure to influenza and/or hypoxia accounts for BW decreases among psychotic cases and controls. Method: Subjects were 111 cases diagnosed with schizophrenia or affective psychosis and 333 matched controls from the Collaborative Perinatal Project. Psychiatric diagnoses were ascertained from medical records. Influenza and hypoxia were determined from maternal and cord sera collected at birth. Results: Cases exposed to severe fetal hypoxia or influenza had significantly lower BW compared with unexposed cases and controls, regardless of exposure status. No significant differences in BW were observed among controls based on exposure status. Conclusions: Decreased BW appears to be a risk factor for psychosis only in the presence of other teratogens. Liability to psychosis likely renders fetuses vulnerable to decreased fetal growth in response to hypoxia and influenza.