Intrauterine growth restriction (IUGR): What it means for your baby

What is IUGR?

Babies are diagnosed with intrauterine growth restriction (IUGR) if they appear to be smaller than expected. This would happen if an ultrasound indicates that the baby's weight is below the 10th percentile for their gestational age (weeks of pregnancy). It's also called fetal growth restriction (FGR).

There are lots of reasons why a baby might appear small. In many cases, a baby who's diagnosed with IUGR just happens to be small (perhaps like one of his parents). And sometimes, a baby who seems small in the womb turns out to be a normal size at birth. But in some cases, something is keeping the baby from growing properly, and the prenatal caregiver will try to figure out if there's a problem and what it is.

How can my caregiver tell how big my baby is?

Your caregiver assesses the size of your uterus during a pelvic exam in your first trimester. After that, she checks your baby's growth by measuring your belly at every prenatal visit. If the measurement (fundal height) is smaller than your due date indicates it should be (this is called "small for dates"), she'll follow up with an ultrasound to pinpoint your baby's size and weight.

You may measure small because your due date (based on your last period) is wrong. This can happen if you remembered the first day of your last period incorrectly or ovulated later than usual in your last cycle. Your doctor will review your earliest ultrasound (which can be used to date a pregnancy) and the date of your period. If they're consistent and your baby is measuring less than the 10th percentile for gestational age, then your baby will be diagnosed with IUGR.

Fetal growth restriction: What causes it?

Other than having a small parent, here are the most common IUGR causes:

• Abnormalities in the umbilical cord or placenta, the organ that delivers oxygen and nutrients to your baby in the womb. The placenta may not be functioning properly if it's too small, improperly formed, or starting to detach from the uterus (placental abruption). A placenta that's too low in the uterus (placenta previa) may slightly increase the risk of IUGR.
• Medical conditions you may have, such as chronic hypertension or preeclampsia (particularly if the preeclampsia is severe and diagnosed in your second trimester or if you have both chronic hypertension and preeclampsia), kidney or heart disease, certain anemias (like sickle cell disease), advanced diabetes, blood clotting disorders, autoimmune disease, antiphospholipid antibody syndrome, or serious lung disease.
• Chromosomal abnormalities, such as Down syndrome, or structural birth defects, such as anencephaly (in which part of the brain is missing) or defects in the kidneys or abdominal wall.
• Carrying twins or higher order multiples.
• Smoking, drinking, or abusing drugs.
• Certain infections your baby may have gotten from you, such as toxoplasmosis, CMV, syphilis, or rubella.
• Certain medications, such as some anticonvulsants.
• Severe malnutrition.

In addition, women who are underweight before pregnancy and don't gain enough weight during pregnancy, and women who live at very high altitudes, are more likely to have somewhat smaller babies.

If you have any of the conditions listed above, you'll have ultrasounds to check your baby's growth, even if your belly measurements during your prenatal visits are normal.

Also, if you've previously had a stillbirth or a baby with IUGR, you can expect at least one ultrasound in your late second or early third trimester to check on your baby's growth.

How will my IUGR baby be affected by the condition?

Babies diagnosed with IUGR are more likely to have certain complications during pregnancy, during delivery, and afterward. The degree of risk depends on what caused the growth problem in the first place, how severe the growth restriction is, how early in pregnancy it starts, and the baby's gestational age at birth.

Research suggests that a baby whose weight is below the 10th percentile is much more likely to have problems than babies who are at or above the 10th percentile. And the risk of both short-term and long-term complications is higher for growth-restricted babies who are also born prematurely.

Growth-restricted babies are at higher risk of:

• Having a c-section delivery, because they have a more difficult time tolerating labor
• Having an abnormally high red blood cell count at birth
• Having low blood sugar, lower resistance to infection, and trouble maintaining their body temperature after birth
• Jaundice
• Meconium aspiration (when the baby inhales his own stool in the womb or during delivery).
• Being stillborn, because of lower levels of oxygen and nutrients in the womb

Will my baby have long-term effects from IUGR?

How a growth-restricted baby will do in the long run depends partly on what caused the growth problem in the first place. Most growth-restricted babies who are otherwise normal do eventually catch up with their peers, although some – particularly those born prematurely – have developmental problems. For example, IUGR has been linked with cerebral palsy.

Finally, some research suggests that growth-restricted babies are more likely to become obese later in life and develop heart disease, type II diabetes, and high blood pressure.

What will happen during pregnancy if my baby has IUGR?

First, you'll have a detailed ultrasound, in part to check your baby's anatomy and see if he has structural defects that may be responsible for his lagging growth. You may also be offered an amniocentesis to check for chromosomal abnormalities, particularly if structural defects were found on an ultrasound or the growth restriction appears severe or was found early in your pregnancy.

Depending on your situation, your caregiver may suggest blood tests or an amniocentesis to see if an infection is the culprit. And you'll be watched carefully for signs of preeclampsia.

Whatever the cause of the IUGR, you'll have regular ultrasounds, often weekly, to check your baby's size and rate of growth since the last ultrasound and to estimate the amount of amniotic fluid in your womb. Your baby will also be monitored with nonstress tests, biophysical profiles, and Doppler ultrasounds (to check blood flow to and from your baby).

Your caregiver may also ask you to do kick counts to keep track of your baby's movements. This is a good way for you to monitor your baby's well-being between prenatal appointments.

Timing of your delivery will depend on how you and your baby are doing. For otherwise uncomplicated IUGR, delivery is at term. But if your baby isn't doing well or you're very sick – with severe preeclampsia, for example – you may have to deliver early.

Is there anything I can do to help my baby who’s been diagnosed with IUGR?

First, keep in mind that IUGR is not your fault, and there is likely nothing you did to cause it. Going forward:

Some caregivers will prescribe bedrest, but there's no evidence that it helps. In fact, the American College of Obstetrics and Gynecology (ACOG) recommends against bedrest for IUGR, as it can cause harm—including blood clots, weakening of your bones, and even depression—without any benefit.

• Be sure to keep all your prenatal and fetal testing appointments.
• If you were planning to deliver at a small community hospital, you may need to transfer to a larger hospital with a neonatal intensive care unit (NICU) that can better handle any problems that might crop up.
• If you smoke, drink alcohol, or use drugs, it's recommended that you give up those activities if you haven't already. (Don't be shy about asking your caregiver to direct you to a program for help.)