Please note: This information was current at the time of publication but now may be out of date.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(2):466-467

See related article on intrauterine growth restriction.

What is intrauterine growth restriction?

Intrauterine growth restriction (“IUGR,” for short) is a term for a baby who is smaller than normal during pregnancy. The baby is not growing inside the uterus at the normal rate. These babies usually have a low weight at birth.

What causes IUGR?

IUGR has various causes. The most common cause is a problem in the placenta (the tissue that carries food and blood to the baby). Birth defects and genetic disorders can cause IUGR. If the mother has an infection, high blood pressure, is smoking, or drinking too much alcohol or abusing drugs, her baby might have IUGR. Sometimes a prescribed medicine that the mother is taking causes IUGR.

Did I cause this problem?

Most of the causes of IUGR are beyond your control. Usually, nothing the mother did causes IUGR in her baby. But if you smoke cigarettes, drink alcohol or abuse drugs, you can cause IUGR in your baby.

Do all small babies have IUGR?

No. About one third of the babies who are small at birth have IUGR. The rest of them don't have IUGR—they're just smaller than normal. Just like there are different sizes of infants, children and adults, there are also different sizes of babies in the uterus. Small babies tend to run in families. The parents or other children in the family may have been small when they were born, too.

How will I know if my baby is just small or has IUGR?

During your pregnancy, your doctor will do tests to find out if your baby is growing normally. The main test for checking a baby's growth in the uterus is an ultrasound. The ultrasound exam lets your doctor see your baby in your uterus with an instrument that is moved across your abdomen (belly).

When the ultrasound exam is done, your doctor will measure the size of your baby's head, abdomen and legs. These measurements will tell you and your doctor if your baby is growing normally. Your doctor will also find out the amount of amniotic fluid in your uterus. In some babies with growth restriction, the amount of amniotic fluid is low. If your baby is small, ultrasound exams may be done more often than usual to check your baby's health.

Are there other tests I might have?

One test is fetal monitoring. It's a way to check your baby's health inside your womb. Straps are put over your uterus as you lie down for about 30 minutes. You will hear your baby's heart beat as it is recorded. Your doctor can look at the heartbeat recording and see if your baby's heartbeat is normal.

You might also have an amniocentesis. A needle is put through your stomach area into your uterus. A few teaspoons of amniotic fluid are withdrawn in the needle. The fluid is tested to see if it shows the cause of the IUGR. The amniotic fluid might show genetic problems or infection.

If my baby has IUGR, will I have to give birth early?

Maybe not. The time of delivery depends on how well your baby is doing. Sometimes, babies with IUGR keep on growing in the uterus. If your baby keeps gaining some weight, an early delivery (before the due date) may not be needed. But if your baby is not growing at all or has other problems, your doctor may decide that an early delivery could help. In this case, your doctor may want to induce labor. Your baby's heart rate and movements will be closely watched to help you and your doctor make this decision.

Will I need to have a cesarean section?

If there are no signs of problems with your baby during labor, a vaginal delivery is OK. Some babies with IUGR are weak. The stress of labor and delivery may be too much for a weak baby. If your baby has problems during labor, a cesarean section (also called a C section) may be safer.

If I have another baby, will that baby also have IUGR?

Generally, no. IUGR usually doesn't occur in another pregnancy. But in some women, it does happen again. Women who have another pregnancy affected by IUGR usually have an illness, such as hypertension, that causes IUGR. Good control of illnesses before and during pregnancy lowers the risk of having another baby with IUGR.

Will my baby need to stay in the hospital longer than usual?

Probably, especially if your baby was born early. Babies who are small at birth need to stay in the hospital until they can breathe and feed normally. After your baby is born, the doctor will check your baby's weight to make sure the baby is growing. Generally, babies stay in the hospital until they weigh about 5 pounds.

Will my baby grow up to be normal in height?

Yes. Your baby will probably catch up in size and have a normal height by about two years of age.

What can I do to help my baby while I'm pregnant?

The best way to help your baby is to pay attention to your baby's movements. Make sure your baby is moving every day. A baby who moves around often is usually healthy. A baby who doesn't move very often or who stops moving may be sick. If you notice your baby isn't moving as much, call your doctor.

Another way you can help your baby is to get a lot of rest. Rest may help you feel better. It may even help your baby grow. Try to get eight hours of sleep (or more) each night. An hour or two of rest in the afternoon is also good for you. Your doctor may even want you to go to the hospital to make sure you rest. The hospital staff will keep a close eye on you and your baby.

Finally, if you smoke, drink alcohol or use drugs, stop now. These things can hurt your baby. This may be all that is needed to improve your baby's health, as well as your own.

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