Perinatal epidemiology--a Nordic challenge.

The focus within perinatal epidemiology has to a large extent been on death and survival as the measures of outcome and less so on measures of morbidity. Too few studies have related perinatal events to measures of health beyond the infancy period, even in the Nordic countries where infant populations may easily be followed through time. Medical birth registries have been established in all the Nordic countries over the period 1967 (Norway) through 1987 (Finland). Unique ID-numbers facilitate linkage within and between these registries as well as record linkages with other data sets. Although outstanding examples of such research exist within perinatal epidemiology, till now we have not taken enough advantage of these valuable sources of data. In the Nordic countries three main areas of perinatal epidemiology would seem to attract considerable attention in the years to come. One area is the study of the association between social factors and adverse outcomes of pregnancy and childbirth. Studies based on record linkages of health registry and census data have recently revealed associations of a kind and magnitude which till now obviously have been disregarded in the Nordic countries. Two other areas of research are longitudinal studies where perinatal exposure is linked with health effects later in life or in later generations. Such studies will be feasible with increasing years of observation of the individuals included in the medical birth registries and the possibilities of generation studies will open up as our registries age.