INTERGROWTH-21st is a large, multicentre, multiethnic, population-based project, involving close to 60 000 deliveries, which aims to produce growth standards from the first trimester through to infancy and improve our understanding of the preterm and impaired fetal growth syndromes. The coordination of the project over eight international centres is a mammoth task and the team are to be congratulated for putting together all the relevant methodological aspects in this issue.
The project will give us more information on how to monitor fetal and neonatal growth against expected growth standards; this may help us to reduce the millions of stillbirths and deaths in infancy that are attributable to poor growth. It is a strong belief that in utero growth is influenced by genes and parental constitution, in addition to environmental factors such as nutrition, smoking and maternal illnesses. The study will elucidate some of the independent contributions of these factors.
Important variables have been standardised to an impressive extent. The period of gestation is based on the last menstrual period, if this was certain and regular, and confirmed by an ultrasound scan in the first trimester when gestational age calculation is most accurate. Identical ultrasound machines and anthropometric equipment have been used across all sites and blinded measurements are taken to minimise the risk of bias. All methods of measurement have also been standardised, which has meant developing an outstanding programme of quality assurance for all the research staff. Mothers are screened before and during pregnancy for illnesses that might influence fetal growth; those with such illnesses will be excluded from the standards. Finally, infants are measured and pregnancy outcomes are ascertained in a similarly standardised manner. The INTERGROWTH-21st Project has been conducted with meticulous attention to detail and has had the resources necessary to achieve these objectives in busy clinical settings.
The detailed information that will be obtained will result in an enormous amount of data on some of the common causes of perinatal deaths, including poor growth and pre-term birth. The INTERGROWTH-21st Project data may be used to investigate some of these devastating pregnancy complications for many years to come.