الفهرس 
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Abstract
Preterm birth (PTB) is defined as any live birth occurring before 37 completed weeks of gestation; this can be subdivided into extremely preterm (<28 weeks), very preterm (28–<32 weeks), moderately preterm (32–<34 weeks) and late preterm (34–<37 weeks) birth based on the gestational age at delivery (Dimes M. 2012). This sub-categorization is important as gestational age is inversely associated with increased mortality, morbidity and the intensity of neonatal care required at birth. Worldwide, 11.1% of infants are born preterm every year (Blencowe H, et al 2012). PTB is the leading cause of perinatal morbidity and mortality and second most common cause of death, after pneumonia, in children under 5 years of age (Lawn JE, et al 2005 and Liu L, et al 2012). Indicated preterm births (iPTB) are those induced for medical reasons, such a pre-eclampsia, intrauterine growth restriction or fetal distress. However, approximately 70% of PTB occur spontaneously The clinical pathways that lead to spontaneous preterm birth (sPTB) typically include preterm labour (PTL) and preterm premature rupture of membranes (PPROM), although these occur on a spectrum and may co-occur in the same clinical setting. PTL is defined as regular contractions and cervical changes at less than 37 weeks gestation and PPROM is defined as spontaneous rupture of membranes at least 1 hour before contractions at less than 37 weeks gestation (Goldenberg RL, et al 2005).