Prematurity was formerly defined by birth weight, that is, less than 5 ½ pounds, regardless of the length of pregnancy. Today, regardless of the birth weight, the gestation age determines the maturity of the baby. This is determined by maternal history, laboratory tests done during the mother’s pregnancy, and physical as well as laboratory tests done on the newborn child. If the gestational age is less than 38 weeks, the baby is known as pre-term; if it is more than 42 weeks, the baby is known as post-term. Between 38 and 42 weeks, the baby is known as term.

If the weight, regardless of the cause, is lower than would be expected from the gestational age, the baby is known as a “low-birth-weight infant:” Thus an infant may be mature but weigh only 1,200 grams, a low-birth weight infant. On the other hand, the baby may have a gestational age of 33 weeks and still weigh only 1,200 grams, an obviously immature or pre-term baby. Mature infants who have a low birth weight must be watched carefully for low blood sugar soon after birth.
Between 7 and 10 percent of all live births are low weight, and these infants are susceptible (in varying degrees, depending upon their maturity) to many diseases, defects, and disorders. Low birth weight can be caused by any of the following: chronic disease in the mother (tuberculosis, diabetes, heart disease); acute infection in the mother; malnutrition of the mother; mother too young or too old; too many children too close together; hereditary factors; mother who smokes a great deal or who takes drugs of any kind (analgesics, sedatives, stimulants, etc.); toxemia of pregnancy; unfavorable living conditions during pregnancy; premature separation of placenta; multiple pregnancy. The low-birth-weight baby may develop perfectly normally or may suffer from any of a wide range of problems-from subtle learning disabilities through severe retardation, blindness, or an ultimately fatal infirmity.

Outlook: The survival chances of the low-birth-weight infant are
directly related to maturity. The lower the gestational age, the higher
the mortality. Immature babies generally show a slower growth and
development than full-term children and tend to lag physically for two
years at least but overcome most of their deficits by school age.
Competent medical care and n loving, protective home are. the two most
important factors in enabling the low-birth-weight baby to grow into a
healthy, normal child.

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