What is preterm birth?
Preterm birth is defined as delivery before 37 weeks of pregnancy have been completed. Generally, preterm birth can be categorized into three subtypes:
．extremely preterm (before 28 weeks)
．very preterm (28 to 32 weeks)
．moderate to late preterm (32 to 37 weeks)
According to the World Health Organization, the rate of preterm birth ranges from 5% to 18% of babies born across the globe. A medical report published by The Chinese University of Hong Kong in 2014 shows that the preterm birth rate in Hong Kong stands at 6.5% in recent years.
Preterm birth is the leading cause of death in newborns, and the second major reason for death in children under the age of 5 after pneumonia. Causes of prematurity remain unknown, but the following risk factors may increase the chance of preterm birth:
．History of miscarriage or preterm delivery
．Uterine abnormalities (e.g. cervical incompetence)
．Teenage mothers or women with advanced maternal age
．Placenta praevia or premature separation of placenta
．Hydramnios or oligohydramnios
．Smoking or alcohol abuse by mother
．Premature rupture of membranes
．Pre-eclampsia of the mother, multiple pregnancy, congenital abnormalities, etc.
