Prematurity or premature birth is defined as the birth of babies who are born before 37 weeks of pregnancy. It is also known as preterm birth. Preterm birth is further divided into three categories which are: extremely preterm (less than 28 weeks) very premature (newborns of 28 to 30 weeks) Moderate to late prematurity (newborns who are born from 32 to 37 weeks)