The term preterm or premature refer to a shortened gestation period and imply incomplete fetal development or immaturity of many body systems. Preterm infants face physical independence before the growth of some of their organs and body tissues is complete. The rate of weight gain in the fetus is greater during the last trimester of pregnancy than any other time. Therefore a preterm infant is often a low birth weight infant as well. With premature birth, the infant is deprived of nutritional support of the placenta during a time of maximal growth.