Low birthweight is when a baby is born weighing less than 5 pounds, 8 ounces. About 1 in every 12 babies in the United States is born with low birthweight.
Some low birthweight babies are healthy, even though they’re small. But being low birthweight can cause serious health problems for some babies.
There are two main reasons why a baby may be born with low birthweight:
Yes. These conditions in the mother may lead to premature birth and/or fetal growth restriction:
This is labor that starts too soon, before 37 completed weeks of pregnancy.
Chronic health conditions
These are health conditions that last for a long time or that happen again and again over a long period of time. Chronic health conditions need treatment from a health care provider. Conditions that may lead to low birthweight include high blood pressure, diabetes and heart, lung and kidney problems.
Certain infections, especially infections in the uterus, may increase your chances of having a premature baby.
Problems with the placenta
The placenta grows in your uterus and supplies your baby with food and oxygen through the umbilical cord. Some problems in the placenta can reduce the flow of blood and nutrients to your baby, which can limit your baby’s growth. In some cases, a baby may need to be born early to prevent serious complications for both mom and baby.
Not gaining enough weight during pregnancy
Women who don’t gain enough weight during pregnancy are more likely to have a low-birthweight baby than women who gain the right amount of weight.
Smoking, drinking alcohol and using street drugs
Pregnant women who smoke cigarettes are nearly twice as likely to have a low-birthweight baby than women who don’t smoke. Smoking slows a baby’s growth and increases your chances of having a premature birth. Using alcohol and street drugs during pregnancy can slow your baby’s growth in the womb and can cause birth defects. Some drugs, like cocaine, may increase your chances of having premature birth.
You’re more likely than other women to have a low-birthweight baby if you:
Yes. These conditions in the baby may lead to premature birth and/or fetal growth restriction:
These are health conditions that are present at birth. Birth defects change the shape or function of one or more parts of the body. They can cause problems in overall health, how the body develops, or in how the body works. They may limit a baby’s development in the womb, which may lead to low birthweight. Babies with birth defects are more likely than babies without birth defects to be born prematurely.
Low-birthweight babies are more likely than babies with normal weight to have health problems as a newborn. Some need special care in a hospital’s newborn intensive care unit (NICU) to treat medical problems like:
Babies born with low birthweight may be more likely than babies born at a normal weight to have certain medical conditions later in life. These include high blood pressure, diabetes and heart disease.
Talk to your baby’s health care provider about what you can do to help your baby be healthy. As your child grows, make sure she eats healthy food, stays active and goes to all her health care checkups. Getting regular checkups throughout childhood can help your provider spot health conditions that may cause problems as your baby grows older. These checkups also help make sure that your child gets all the vaccinations she needs to stay protected from certain harmful diseases.
Learn what you can do to get healthy before and during pregnancy to help reduce your risk of having a low-birthweight baby and improve your chances of having a healthy pregnancy and a healthy baby.
Last reviewed September 2012
Chronological age is the age of a baby from the day of birth. Adjusted age is the age of the baby based on his due date. To calculate adjusted age, take your baby's chronological age (for example, 20 weeks) and subtract the number of weeks premature the baby was (6 weeks). This baby's adjusted age (20 - 6) is 14 weeks. Health care providers may use this age when they evaluate the baby's growth and development. Most premature babies catch up to their peers developmentally in 2 to 3 years. After that, differences in size or development are most likely due to individual differences, rather than to premature birth. Some very small babies take longer to catch up.
Late preterm means that a baby is born after 34 weeks but before 37 weeks of pregnancy. It's important to try to have your baby as close to 39 weeks of pregnancy as possible. In the last few weeks of pregnancy, your baby's organs, like his brains, lungs and liver, are still growing. Waiting until you're at least 39 weeks also gives your baby time to gain more weight and makes him less likely to have vision and hearing problems after birth. Your baby will also be better able to suck and swallow and stay awake long enough to eat after he's born. Babies born early sometimes can't do these things.