The epidemiology of preterm birth.

Preterm birth is a major clinical problem, accounting for 47% of all neonatal deaths. The preterm delivery rate in UK is approximately 7%, and rates of preterm birth are steadily increasing. The diagnosis of preterm labour is difficult and most interventions to halt labour are unsuccessful. Despite this, the lack of good data hinders high quality research. The West Midlands has the highest perinatal mortality in the UK and a Perinatal Institute was set up in 2000 to address this, and aid improvements in care. Survival rates amongst preterm infants have changed dramatically over the last decade, with 88% survival for 2728 weeks, and 21% for > or =24 weeks (depending on birth weight). Risk factors include lower social class, less education, single marital status, low income, younger maternal age, low body weight, ethnicity, smoking, poor housing along with medical factors such as induction, premature rupture of membranes, infection, multiple pregnancy intrauterine death, fetal and uterine abnormalities and chorioamnionitis. Data from further detailed, robust studies are required to facilitate a comprehensive understanding of risk factors and their relationship with each other. Only then will it be possible to influence the adverse outcomes described.