Some aspects of birth seasonality in Kenya.

Seasonal variations in vital events have been widely observed in temperate and sub-tropical regions. Because of the more equable range of temperatures, less work on seasonality has been done in the tropics. In Kenya, a tropical country with a variety of ecological conditions, data on registered births gathered at district level for a period of 42 months suggest that, for the country as a whole, month to month variations in the numbers of births display a measure of seasonal regularity with a major peak in September and a subsidiary one in April-May. The pattern is repeated in several districts and the evidence points to the influence of holiday months, harvest times and, particularly at the coast, climatic variables, as underlying the observed patterns. Autoregressive modelling confirms the regularity of seasonal patterns in many districts and a closer study of the interaction of conceptions and climatic variables suggests the possibility of a positive association between conception rates and food availability. Some implications of regular seasonality in births on health policy are discussed.