Preterm labour is defined as the delivery of the fetus when birth occurs between 20 and 37 completed weeks.

Preterm labour is one of the major causes of neonatal mortality (1–5 per cent) and morbidity (necrotising enterocolitis; retinopathy of prematurity, intraventricular haemorrhage; chronic lung disease; cerebral palsy, blindness and learning difficulties; and developmental delay).

It is estimated that 40 per cent of preterm labours are due to infections that can be prevented if detected and treated early. The earlier the preterm birth, the more it is due to infection. Preterm birth is the most frequent cause of infant death in the United States, accounting for at least one-third of infant deaths in 2002.

In many cases, the reasons for preterm labour are largely unknown. In other instances, preterm labour can have a variety of different causes, e.g. infection, an ‘incompetent’ or weak cervix, multiple pregnancy, history of certain types of surgery on the uterus or cervix, lifestyle factors such as low pre-pregnancy weight, obesity, smoking during pregnancy and substance abuse.

This chapter will focus on inflammatory and infectious conditions.