Low Birth Weight
Summary
What is low birth weight?
Low birth weight is a term used to describe babies who are born weighing less than 5 pounds, 8 ounces (2,500 grams). An average newborn usually weighs about 8 pounds. A low-birth-weight baby may be healthy even though he or she is small. But a low-birth-weight baby can also have many serious health problems.
What causes low birth weight?
Low birth weight is most often caused by being born too early (premature birth). That means before 37 weeks of pregnancy. A premature baby has less time in the mother’s womb (uterus) to grow and gain weight. Much of a baby’s weight is gained during the last weeks of pregnancy.
Another cause of low birth weight is a condition called intrauterine growth restriction (IUGR). This occurs when a baby does not grow well during pregnancy. It may be because of problems with the placenta, the mother’s health, or the baby’s health. Babies can have IUGR and be:
- Full term. That means born from 37 to 41 weeks of pregnancy. These babies may be physically mature, but small.
- Premature. These babies are both very small and physically immature.
Source: Stanford Medicine (n.d.). Low Birth Weight.