Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. 

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Am Fam Physician. 1998;58(6):1393-1394

See related article on intrauterine growth retardation.

What is IUGR?

IUGR stands for intrauterine growth retardation. This means that your baby is growing slowly and doesn't weigh as much as your doctor expected for this stage of pregnancy. If your unborn baby weighs less than most babies at this stage, your baby might have IUGR. IUGR is also used to describe a baby who weighs less at birth than most babies at the same stage. For babies who are born near their due date (meaning, they aren't premature), the dangerous weight is anything less than 5 pounds, 8 ounces.

Your doctor might suspect IUGR if he or she thinks your baby is growing slightly less than would be expected. IUGR is usually diagnosed during an ultrasound examination. Doctors most often find it during the 6th, the 7th or the 8th months of pregnancy.

It's important to know that IUGR only means slowed growing. These small babies aren't mentally slow or retarded. Most small babies grow up to be healthy children and adults.

Why is my baby small?

Doctors know many of the causes of IUGR but are only able to be sure about the cause in about one half of babies who have IUGR. The most common reasons for a baby to be small are the following:

  • The mother smoked cigarettes during pregnancy.

  • The mother drank alcohol during pregnancy.

  • The mother had high blood pressure during pregnancy.

  • The mother had infections during pregnancy.

  • The baby has chromosomal abnormalities (like Down syndrome).

  • The mother used certain medicines during pregnancy.

  • The mother is small (less than 5 feet tall or weighing less than 110 pounds).

Why is my baby's size important?

The best predictor of a baby's survival and good health is its birth weight. Babies born with low birth weight might have problems near the time of birth. Because of the danger of some of these problems—such as difficulty holding a normal body temperature or fighting infection—your doctor will do some tests to find out if your baby is growing well, both before and after birth.

What tests might be done on my baby?

Two tests can find out if your baby has IUGR and keep track of your baby's growth in the womb. These tests are the ultrasound exam and the nonstress test. The first kind of test, the ultrasound exam, is used to find out if your baby has IUGR. This exam is done every three to four weeks to make sure your baby is still growing right. The ultrasound exams let your doctor look at your baby's internal organs and measure the amount of fluid around the baby.

Special ultrasound exams are called biophysical profiles. During a biophysical profile, the person who does the exam will also watch your baby's breathing, muscle tone and movements.

The other test is the nonstress test. This test is usually done in the doctor's office, but it might be done in a hospital. A nonstress test measures how fast your baby's heart is beating. A healthy baby normally has a heartbeat that gets faster as the baby moves around. A nonstress test takes about 20 to 30 minutes to do. It might take longer if your baby is asleep.

Sometimes your doctor wants to watch your baby's heartbeat while your uterus contracts (squeezes together). This is called a contraction stress test. There are two ways to help you have contractions for just a little while. First, your nipples will be warmed up. Sometimes this makes your uterus start contracting for a little while. If that doesn't work, you could take a special medicine (either oxytocin or pitocin), to make your uterus contract just for a little while.

What happens if a test isn't normal?

If one of the tests isn't normal, your doctor may want to do other tests. Your doctor may also try to start your labor early (induce labor) if you might have a problem.

What will the doctor do to help my baby?

If your baby is very small when it's born, your doctor can give it oxygen through a nose tube, fluids through a tube in a vein and, sometimes, antibiotics.

What can I do to help my baby?

You can do five important things to help your baby grow big enough before it's born:

  1. If you smoke—quit now. Cigarettes hurt the placenta, which is your baby's only way to get “food.” It's never too late to quit smoking. Babies gain one half of their weight in the last three months before being born.

  2. If you drink alcohol—quit now. Even one drink a day makes it more likely that you will have a small baby. You could even have a baby with brain damage caused by the alcohol. This can happen in all months of pregnancy.

  3. If you use illegal drugs—quit now. Almost all illegal drugs make babies too small to be strong and healthy. You may need your doctor's help to quit so you don't have withdrawal problems.

  4. Eat a good diet. Ask your doctor to tell you the best foods to eat.

  5. Keep all your appointments for doctor visits and tests.

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