Why did the stillbirth rate decline in Denmark after 1940?

Stillbirth rates began declining in several industrialized countries simultaneously at the beginning of the 1940s. The reasons for this sudden decline have been discussed ever since. Changes in obstetric care, in risk factors, and in the composition of the population at risk have been suggested. One hypothesis is that it reflects a cohort effect of improved reproductive health status among women born during the first decades of the twentieth century arising from the decline in fertility. Other hypotheses point towards improved antenatal and obstetric care and changes in the prevalence of different risk factors. In this study, all death certificates for the stillborn in Denmark during 1938, 1941, 1945, and 1949 were used to investigate the different hypotheses. As possible contributing factors, the results suggest improvements in relation to the course of the delivery, changed parity distribution, and a cohort effect.