Very Low Birth Weight
What is very low birth weight?
Very low birth weight (VLBW) is a term used to describe babies who are born weighing
less than 3 pounds, 4 ounces (1.5 kilograms). It is very rare that babies are born
this tiny. Only about 1% of babies born in the U.S. are very low birth weight.
What causes very low birth weight?
The main cause of a baby having VLBW is being born too early. This is called preterm
or premature birth. Premature means a baby is born before 37 weeks of pregnancy. Very-low-birth-weight
babies are often born before 30 weeks of pregnancy. A premature baby has less time
in the pregnant person’s uterus to grow and gain weight. Much of a baby's weight is
gained during the later part of pregnancy.
Another cause of very low birth weight is when a baby does not grow well during pregnancy. This
is called fetal growth restriction (FGR). In the past, this was called intrauterine
growth restriction. It may happen because of problems with the placenta, the pregnant
person's health, or birth defects. Most very low birth weight babies who have FGR
are also born early. They are usually very small and physically immature.
Who is at risk for very low birth weight?
A baby is more likely to be very low birth weight if they are premature or have had
fetal growth restriction. Other things that happen to or with the pregnant person
can increase the risk for VLBW, growth restriction, and prematurity. They include:
Having an infection during pregnancy
Not gaining enough weight during pregnancy
Having a previous pregnancy with a low-birth-weight baby
Using alcohol or illegal drugs
Being younger than age 17 or older than age 35
Being African American
What are the symptoms of very low birth weight?
Babies with very low birth weight look much smaller than babies of normal birth weight.
A very-low-birth-weight baby's head may look big compared with the rest of their body.
A baby with VLBW often looks very thin with little body fat. Blood vessels can be
easily seen through the skin.
How is very low birth weight diagnosed?
One of the main reasons for regular prenatal exams is to make sure your unborn baby
is growing well. During pregnancy, the size of your baby is estimated in different
ways. Your steady weight gain is 1 way of checking on the baby’s growth.
Another way is to measure the top of your uterus from the pubic bone (fundal height).
The number of centimeters measured is usually the same or close to the number of weeks
of pregnancy. If the fundal height measurement is low for the number of weeks you
are pregnant, it may mean that your baby is not growing well.
Other ways to check the baby’s growth are:
Using ultrasound to estimate the baby’s growth and development. Your healthcare provider
can use measurements of your baby's head, belly, and upper leg bone to estimate their
Comparing your baby’s estimated birth weight with their gestational age. The provider
may use a formula to figure out your baby’s body mass.
A birth weight of less than 5 pounds, 8 ounces (2.5 kilograms) is called low birth
weight. Babies weighing less than 3 pounds, 4 ounces (1.5 kilograms) at birth are
considered very low birth weight.
How is very low birth weight treated?
Treatment will depend on your child’s symptoms, age, and general health. It will also
depend on how severe the condition is. Babies with VLBW need:
Care in the neonatal intensive care unit (NICU)
Special feedings, most often with a tube into the stomach as well as IV fluid
Other treatments for possible complications
The outcome for a baby with VLBW depends mainly on how much the baby weighs and how
many weeks of gestation the baby is at birth. The smallest and earliest babies have
the most problems. They are less likely to survive.
Babies with VLBW may have a harder time catching up in physical growth because they
often have other problems. Many very-low-birth-weight babies are referred to special
follow-up healthcare programs.
What are possible complications of very low birth weight?
Babies with a very low birth weight have a greater risk of developing problems. Their
tiny bodies are not as strong as babies of normal weight. They may have a harder time
eating, gaining weight, and fighting infection. They have very little body fat. So
they often have trouble staying warm in normal temperatures.
Most babies with a very low birth weight are also premature. This can make it hard
to separate the problems caused by the prematurity from the problems of just being
so tiny. In general, the lower the baby's birth weight, the greater the risks for
complications. Here are some possible problems for babies with VLBW:
Low blood sugar levels at birth
Retinopathy of prematurity, an eye disorder that can cause blindness
Low oxygen levels at birth
Trouble staying warm
Trouble feeding and gaining weight
Breathing problems because of immature lungs (respiratory distress syndrome)
Nervous system problems, such as bleeding inside the brain or damage to the brain’s
Serious digestive problems, such as necrotizing enterocolitis
Very-low-birth-weight babies need special care in the NICU until they can gain weight
and are well enough to go home.
Risks for long-term problems and disability are increased for babies with VLBW. Long-term
complications may include:
Cerebral palsy or difficulty with movement
Blindness or difficulty with vision (for example, may need glasses)
Deafness or difficulty with hearing (for example, may need hearing aids)
Developmental delay including behavioral, emotional, and/or learning problems
Talk with your baby's healthcare provider about your baby’s risks for complications.
Ask about what can be done to take care of these as early as possible. Also ask whether
your child will need checkups or screening as they grow up.
Can very low birth weight be prevented?
There have been advances in the care of sick and premature babies. More babies today
survive even though they are born early and very small. But preventing preterm births
is 1 of the best ways to prevent very low birth weight.
Regular prenatal care is the best way to prevent preterm births and very-low-birth-weight
babies. At prenatal visits, your health and the health of your unborn baby are checked.
It is important to:
Follow a healthy diet during pregnancy. This will help you gain enough weight to help your baby grow and help you stay healthy.
Stay away from alcohol, cigarettes, or illegal drugs. All of these can cause low birth weight and other problems for your baby.
Key points about very low birth weight
Very low birth weight is a term used to describe babies who are born weighing less
than 3 pounds, 4 ounces (1.5 kilograms).
The main cause of very low birth weight is being born too early, called premature
Treatment for very low birth weight babies includes care in the NICU, temperature-controlled
beds, and special feedings.
In general, the lower the baby's birth weight, the greater the risks for complications.
Prenatal care is a key factor in preventing preterm births and very low birth weight.
Tips to help you get the most from a visit to your child’s healthcare provider:
Know the reason for the visit and what you want to happen.
Before your visit, write down questions you want answered.
At the visit, write down the name of a new diagnosis, and any new medicines, treatments,
or tests. Also write down any new instructions your provider gives you for your child.
Know why a new medicine or treatment is prescribed and how it will help your child.
Also know what the side effects are.
Ask if your child’s condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if your child does not take the medicine or have the test or procedure.
If your child has a follow-up appointment, write down the date, time, and purpose
for that visit.
Know how you can contact your child’s provider after office hours. This is important
if your child becomes ill and you have questions or need advice.