The proportion of infants under one month of age who die. In England and Wales this has fallen markedly in recent decades: from more than 28 per 1,000 live births in 1939 to 2.8 in 2012. This improvement can be attributed to better antenatal supervision of expectant mothers, including ensuring they have adequate nourishing food; improvements in the management of the complications of pregnancy and of labour; and more skilled resuscitation at birth for those babies who need it.

Nearly three-quarters of neonatal deaths occur during the first week of life. In Britain, in the last four decades of the 20th century, the number of deaths in the first week of life fell dramatically from 13.2 to just over 1 per 1,000 live births. The chief causes of deaths in this period are extreme prematurity (less than 28 weeks’ gestation), birth asphyxia with oxygen lack to the brain, and congenital abnormalities. After the first week the commonest cause is infection.