Abstract
Comparisons of mortality and rates of cerebral palsy in different populations can be confusing. This is illustrated by comparing two populations of very low birthweight infants born in the 1980s, one from the Netherlands, the other from the UK (Oxford region). Although a number of biases were controlled for while comparing two large geographically defined populations, by assessing the survivors at similar ages and describing their health status in a standard way, some problems in interpretation of outcome remained. Differences in registration practice of live births at early gestational ages, as well as differences in withholding or withdrawing treatment, which occurred in about half of the cases of neonatal death in the Netherlands and in about one third of those in the Oxford region, may have influenced the incidence of registered live births, neonatal mortality, and the rate of cerebral palsy.