An understanding of the basic patterns in the seasonality of birth rate may be useful in certain fertility techniques. The use of artificial birth control, however, has had the effect of masking the influence of underlying biometeriological factors. To elucidate trends in birth seasonality in the absence of current social factors, a study useing nineteenth-century parish records was undertaken. Analysis of 5,905 births recorded in the baptismal records of the parishes of Hawarden and Northop between the years 1837 and 1886 revealed significant seasonal trend with a peak occuring in the spring. Further analysis showed a significant positive correlation occuring between the (standardized) numbers of births in each month and the mean day length (hours between sunrise and sunset) of the pulative month of conception
