Abstract
The development of 43 infants born at full term, who were admitted to neonatal intensive care units shortly after birth, was compared in a prospective longitudinal study with that of a group of 29 healthy newborn babies. Thirty infants required emergency operations during the neonatal period, and 13 were admitted for medical reasons. The effects of being in hospital and being separated from their mothers were also studied. At 1 year the 'sick' babies were performing significantly less well in almost all areas of development. In the group of sick infants, the mothers' mental health explained 25% of the variance in developmental outcome at 6 months. At 1 year the most important predictor was length of stay in hospital, which explained 35% of the variance.