A statistical analysis of the annual pattern in white births of maternal age groups in the United States for the years 1973 thru 1980

Abstract

Abstract The annual trend of white births of maternal age groups in the United States was analyzed for the years 1973 thru 1980. Monthly means for each age group were subjected to time series analysis with sine curves, using a stepwise, forward‐going regression analysis. The births in the maternal age groups also were compared with an analysis of variance in order to detect differences in trend. Adjacent age groups exhibited different annual trends. The general pattern of births for the period of 12 months was bimodal. The youngest and oldest maternal groups exhibited approximately equal peaks. In the middle age groups the bimodal peaks were unequal, with a major peak in September and a minor peak in February or March. Other smaller differences were present that characterized each of the eight maternal age groups, and minor changes in the annual trends occurred within the period of the study for three of the eight age groups. The relevance of maternal age groups to the peak shift from August to September ...