Observations on single births to women resident in Belfast 1962–1966 part II. Factors associated with postperinatal mortality

Abstract An investigation into several selected biosocial factors affecting perinatal mortality was made based on all single (live and still) births, 42,279, and related singleton perinatal deaths, 1468, occurring to women resident in Belfast, Northern Ireland, during a 5-yr period of observation—1962–1966. The data were examined by unifactor and multifactor analyses. The relative contributions to perinatal mortality risk and the confounding effects between several biosocial factors were studied in detail using a binary multiple regression model. A multi-factor model containing seventeen factors explained 46.5 per cent of the total variation in perinatal mortality risk while a model containing one factor only, birthweight, explained 42.7 per cent. It was concluded that birthweight is the most important single factor determining fatal or nonfatal outcome during the perinatal period. The relative contributions of such factors as maternal age, parity and social class, although significant, were small in comparison. The findings were discussed in relation to previous studies and with respect to the use of risk evaluation models in determining obstetric care.