Definition of Premature birth

Premature birth (also known as a preterm birth) is the birth of a baby before the standard period of pregnancy is completed. In most systems of human pregnancy, prematurity is considered to occur when the baby is born sooner than 37 weeks after the beginning of the last menstrual period (LMP). The standard length of a human gestation is 266 days, however, for convenience most timing is based on the LMP, with conception being assumed to occur approximately 14 days after the LMP, making a standard term pregnancy 280 days or 40 weeks. The opposite condition, postmature birth, is defined as birth more than 42 weeks after the LMP.