Background:Complex seasonal variations in abortions and seasonal trends have been reported worldwide, but there are no data from Australia.Material/Methods:Hospital morbidity and birth data were modelled using time series and regression techniques to describe seasonal changes in births and abortions (1989–99) in NSW, Australia. Data were also analysed to determine demographic predictors of abortions.Results:A higher proportion of births in NSW were recorded in March and September-October. Irrespective of the nuptiality the lowest seasonal indices were recorded in February and November. For married women aged 20–49 years, voluntary abortions were significantly higher in February (t=0.04) and significantly lower in April (t

Keywords: Abortion, Induced - statistics & numerical data, Abortion, Induced - trends, Abortion, Spontaneous - epidemiology, Adolescent, Birth Rate - trends, Child, Infant, Newborn, Marital Status, New South Wales - epidemiology, Pregnancy, Seasons