Intrauterine Growth Restriction (IUGR)

What is intrauterine growth restriction (IUGR)?

Intrauterine growth restriction (IUGR) is a term used to describe a condition in which the fetus is smaller than expected for the number of weeks of pregnancy. Another term for IUGR is fetal growth restriction. Newborn babies with IUGR are often described as small for gestational age.

A fetus with IUGR often has an estimated fetal weight less than the 10th percentile. This means that the fetus weighs less than 90 percent of all other fetuses of the same gestational age. A fetus with IUGR may be born at term (after 37 weeks of pregnancy) or prematurely (before 37 weeks).

Newborn babies with IUGR often appear thin, pale, and have loose, dry skin. The umbilical cord is often thin and dull-looking rather than shiny and fat. Some babies do not have this malnourished appearance but are small all-over.

What causes intrauterine growth restriction (IUGR)?

Intrauterine growth restriction results when a problem or abnormality prevents cells and tissues from growing or causes cells to decrease in size. This may occur when the fetus does not receive the necessary nutrients and oxygen needed for growth and development of organs and tissues, or because of infection. Although some babies are small because of genetics (their parents are small), most IUGR is due to other causes. Some factors that may contribute to IUGR include the following:

  • Maternal factors:

    • High blood pressure

    • Chronic kidney disease

    • Advanced diabetes

    • Heart or respiratory disease

    • Malnutrition, anemia

    • Infection

    • Substance abuse (alcohol, drugs)

    • Cigarette smoking

  • Factors involving the uterus and placenta:

    • Decreased blood flow in the uterus and placenta

    • Placental abruption (placenta detaches from the uterus)

    • Placenta previa (placenta attaches low in the uterus)

    • Infection in the tissues around the fetus

  • Factors related to the developing baby (fetus):

    • Multiple gestation (for example, twins or triplets)

    • Infection

    • Birth defects

    • Chromosomal abnormality

Why is intrauterine growth restriction (IUGR) a concern?

IUGR can begin at any time in pregnancy. Early-onset IUGR is often due to chromosomal abnormalities, maternal disease, or severe problems with the placenta. Late-onset growth restriction (after 32 weeks) is usually related to other problems.

With IUGR, the growth of the baby's overall body and organs are limited, and tissue and organ cells may not grow as large or as numerous. When there is not enough blood flow through the placenta, the fetus may only receive low amounts of oxygen. This can cause the fetal heart rate to decrease placing the baby at great risk.

Babies with IUGR may have problems at birth including:

  • Decreased oxygen levels

  • Low Apgar scores (an assessment that helps identify babies with difficulty adapting after delivery)

  • Meconium aspiration (inhalation of the first stools passed in utero), which can lead to difficulty breathing

  • Hypoglycemia (low blood sugar)

  • Difficulty maintaining normal body temperature

  • Polycythemia (too many red blood cells)

Severe IUGR may result in stillbirth. It may also lead to long-term growth problems in babies and children.

How is intrauterine growth restriction (IUGR) diagnosed?

During pregnancy, fetal size can be estimated in different ways. The height of the fundus (the top of a mother's uterus) can be measured from the pubic bone. This measurement in centimeters usually corresponds with the number of weeks of pregnancy after the 20th week. If the measurement is lower than expected, an ultrasound is needed to get an estimated fetal size and to diagnose IUGR.

Other diagnostic procedures may include the following:

  • Ultrasound. Ultrasound (a test using sound waves to create a picture of internal structures) is a more accurate method of estimating fetal size. Measurements can be taken of the fetus' head and abdomen and compared with a growth chart to estimate fetal weight. The fetal abdominal circumference is a helpful indicator of fetal nutrition.

  • Doppler flow. Another way to assess fetal well-being once IUGR has been diagnosed is Doppler flow, which uses sound waves to measure blood flow. The sound of moving blood produces wave-forms that reflect the speed and amount of the blood as it moves through a blood vessel. Blood flows through vessels in the both the fetal brain and the umbilical cord  can be checked with Doppler flow studies.

  • Mother's weight gain. A mother's weight gain can also indicate a baby's size. Small maternal weight gains in pregnancy may correspond with a small baby, but not always.

How is intrauterine growth restriction (IUGR) managed?

Management of IUGR depends on the severity of growth restriction, and how early the problem began in the pregnancy. Generally, the earlier and more severe the growth restriction, the greater the risks to the fetus. Careful monitoring of a fetus with IUGR and ongoing testing may be needed.

Some of the ways to watch for potential problems include the following:

  • Fetal movement counting. Keeping track of fetal kicks and movements. A change in the number or frequency may mean the fetus is under stress.

  • Nonstress testing. A test that watches the fetal heart rate for increases with fetal movements, a sign of fetal well-being.

  • Biophysical profile. A test that combines the nonstress test with an ultrasound to evaluate fetal well-being.

  • Ultrasound. A diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels. Ultrasounds are used to follow fetal growth.

  • Doppler flow studies. A type of ultrasound that uses sound waves to measure blood flow.

Treatment for IUGR

Although it is not possible to reverse IUGR, some treatments may help slow or minimize the effects. Specific treatments for IUGR will be determined by your doctor based on:

  • Your pregnancy, overall health, and medical history

  • The extent of the disease

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the disease

  • Your opinion or preference

Treatments may include:

  • Nutrition. Some studies have shown that increasing maternal nutrition may increase gestational weight gain and fetal growth.

  • Bedrest. Bedrest in the hospital or at home may help improve circulation to the fetus.

  • Delivery. If IUGR endangers the health of the fetus, then an early delivery may be necessary.

Prevention of intrauterine growth restriction

Intrauterine growth restriction may occur, even when the mother is in good health. However, some factors may increase the risks of IUGR, such as cigarette smoking and poor maternal nutrition. Avoiding harmful lifestyles, eating a healthy diet, and getting prenatal care may help decrease the risks for IUGR. Early detection may also help with IUGR treatment and outcome.