Regional variations in seasonality of births in Nigeria, 1990-2007: A trigonometric regression model approach

Background: Seasonality of births in Nigeria has been previously addressed in a small number of studies. This study was designed to explore and describe the regional variations in the seasonality of births in Nigeria. Data Source and Methods: A total of 82,827 births history data collected in the Nigerian Demographic Survey 2008 were analyzed. It covered periods between January 1990 and December 2007. Seasonal variation by month of birth was explored with the aid of correlogram. A classical time series trigonometric regression model was fitted to describe the pattern of seasonality. Findings: The reported monthly distribution for number of births showed a significant seasonal pattern with a peak in May and corresponding minima in November. Birth patterns differ across the regions, but in every region, births are concentrated in the first half of the year. Conclusion: Though, birth seasonality is more pronounced in the northern part of the country, there has been significant shift in the magnitude of variation in the 18 year period of study.