A note on the influence of factors early in development on later reproductive function.

Historical trends for stillbirth rates in Norway are used to study the possible effect of suboptimal conditions early in life upon later reproductive function. A comparison of the trend for the stillbirth rate and the trend for mortality reveals some clear differences. While the mortality shows a steadily falling trend from the turn of the century, the stillbirth rates show a plateau from 1900-1910 to about 1935. Standardized stillbirth rates are computed from age-specific stillbirth rates (which are available for certain five-year intervals from 1880 onwards), and these rates are used to investigate whether a better correspondence between the trends can be obtained by ascribing the stillborn children to the year of the mother's birth, rather than to the year of the stillbirth. The correspondence appears to be clearly improved by ascribing the stillbirths to the mother's birth year. This observation is discussed in relation to other observations providing information on the importance of conditions during early life on the development and function of the reproductive system.