Very low birthweight babies are often born before 30 weeks of pregnancy. Being born early means a baby has less time in the mother s uterus to grow and gain weight. Much of a baby s weight is gained during the latter part of pregnancy. This is when a baby does not grow well during pregnancy because of problems with the placenta, the mother s health, or birth defects. Most very low birthweight babies who have IUGR are also born early, and are both very small and physically immature.
Any baby born prematurely is more likely to be very small.
However, there are other factors that can also contribute to the risk of very low birthweight. Over half of twins and other multiples have very low birthweights. Mothers of lower socioeconomic status are also more likely to have poorer pregnancy nutrition, inadequate prenatal care, and pregnancy complications - all factors that can contribute to very low birthweight. A baby with very low birthweight is often at increased risk for complications. Because they have so little body fat, very low birthweight babies often have difficulty staying warm in normal temperatures.