Preterm birth occurs in about 5% to 10% of all births in resource-rich countries, but in recent years the incidence seems to have increased in some countries, particularly in the USA. We found little reliable evidence for incidence in resource-poor countries. The rate in northwestern Ethiopia has been reported to vary from 11% to 22%, depending on the age group of mothers studied, and is highest in teenage mothers.We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of preventive interventions in women at high risk of preterm delivery? What are the effects of interventions to improve neonatal outcome after preterm rupture of membranes? What are the effects of treatments to stop contractions in preterm labour? What are the effects of elective compared with selective caesarean delivery for women in preterm labour? What are the effects of interventions to improve neonatal outcome in preterm delivery? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2010 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).We found 58 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.In this systematic review, we present information relating to the effectiveness and safety of the following interventions: amnioinfusion for preterm rupture of membranes, antenatal corticosteroids, antibiotic treatment, bed rest, beta-mimetics, calcium channel blockers, elective caesarean, enhanced antenatal care programmes, magnesium sulphate, oxytocin receptor antagonists (atosiban), progesterone, prophylactic cervical cerclage, prostaglandin inhibitors (e.g., indometacin), selective caesarean, and thyrotropin-releasing hormone (TRH) (plus corticosteroids).