Spontaneous preterm birth remains the leading cause of neonatal death, and the second leading cause of mortality worldwide in children below five years of age. The causes of preterm birth are multifactorial, likely contributing to why significant progress in reducing the incidence has been slow. This Element contains the most up-to-date evidence regarding the aetiology, epidemiology, and management of pregnancies at risk of, or complicated by, spontaneous preterm birth and preterm pre-labour rupture of membranes. It concentrates largely on those aspects potentially amenable to preventative intervention (i.e. cervical dysfunction and premature uterine contractility), as well as strategies to improve outcomes for infants born prematurely.