Assessing quality of NHS Numbers for Babies data and providing gestational age statistics.

This paper investigates the quality of information in the National Health Service (NHS) Numbers for Babies (NN4B) dataset and provides statistics on gestational age at birth in relation to live/stillbirth status, multiple birth status, age of mother, babies' sex, and birthweight. Gestational age information is not recorded at the registration of live births and the NN4B system provides the opportunity to access this information for all live and stillbirths in England and Wales. All NN4B records for babies born in England and Wales in 2005 were used in this analysis. Data quality was generally good although some aspects need further investigation. The gestational age data are credible, consistent with other U.K. data sources, and the statistics by maternal age, multiplicity and sex are as expected. These data, previously unavailable for England and Wales as a whole, provide a reference against which to monitor trends in preterm births and can inform the planning of neonatal care provision. NN4B is a powerful new data source which can extend