Definition of prematurity:
Is all premature birth that occurs before 37 weeks of gestation. so it's about of 35 weeks pregnant.
Within this overall prematurity, we must distinguish an average prematurity (33 weeks to 36 weeks + 6 days), high prematurity (32 weeks to 28 + 6 days) and extreme prematurity (before 28).
Duration of a pregnancy : 41 weeks of amenorrhea , or 39 weeks of pregnancy.
(source: sosprema DOT com)