It occurs when a baby is delivered before 36 weeks of pregnancy. Factors that lead to premature labor are e.g. premature rupture of your membranes, weak cervix, and placenta separation. The baby is not yet ready to face life outside the mother’s uterus in terms of respiration, temperature control and bleeding, liver function and infections. So the babies are kept in special incubators for a period of time till they are ready.