Declining mortality in the immature: medical or biological effect?

A steady and significant decline in the proportions of liveborn infants who died in the first week from problems associated with immaturity occurred among Sheffield babies born between 1947 and 1979. The decline occurred in all three maternity units, regardless of the availability of neonatal care facilities. The rate of decline in the best equipped and best staffed hospital, however, was significantly greater during the 1970s than would have been predicted from the trend in earlier years and in contrast to the other hospitals. This greater decline shows a closer temporal association with a reorganisation of labour wards and nurseries than with the introduction of advanced equipment but also correlates with an increasing abortion rate among women who would be expected to have premature deliveries. Factors responsible for the secular decline have not been identified, but it is postulated that Sheffield's mothers are bearing healthier children as a result of improvements in maternal health which are themselves a consequence of changes during girlhood.