Perhaps the biggest concern in providing human milk to premature infants is growth. Term infants undergo rapid growth in the third trimester of pregnancy receiving nutrition through the placenta and swallowed amniotic fluid with no need to expend calories for temperature regulation or gas exchange. Premature infants miss out on much or all of the third trimester and thus have higher nutritional requirements on a per kilogram basis than term infants. Human milk evolved/was designed to nourish the term infant who can tolerate large fluid volumes, whereas premature infants are less tolerant of high fluid volumes.