Question: What is the definition of postmature? Multiple choice question. A fetus not yet born as of 42 weeks' gestation Infants whose birth weight is less than that of 90% of babies of the same gestational age as a result of slow fetal growth Infants born before completing the 37th week of gestation Infants who weigh less than 5½ pounds at birth because of prematurity or being small-for-date