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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 ranges

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.