BackgroundTo assess quarterly fluctuations in schizophrenia births in a southern hemisphere data set, and to compare the quarterly birth distributions of patients born in the northern and southern hemisphere.MethodThe month and place of birth of patients with schizophrenia (n = 9348) were extracted from a mental health register.ResultsThe quarterly birth distribution of patients with schizophrenia differed significantly from the estimated general population distribution in SH-born patients. The quarterly distribution of patient births differed significantly when the two hemispheres were compared.ConclusionThese data support the hypothesis that there is a risk for schizophrenia that is related to the time of birth, and which fluctuates across the year.