<prompt> Extreme preterm is defined as34-36 weeks32-33 weeks28-31 weeks28 weeks  <response>: Preterm labor is defined as one where the labor stas before 37th completed week, counting from the first day of the last menstrual period Lower limit of gestation is - 20 weeks in developed countries 28 weeks in developing countries Ref: Dutta Obs 9e pg 294. 