What Is Intrauterine Growth Restriction (IUGR)?

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During pregnancy, prenatal care visits become an integral part of your routine. Once you reach 20 weeks pregnant, your provider will begin tracking your baby's size to check for intrauterine growth restriction (IUGR).

They will do this by measuring the fundal height—or the distance in centimeters from the top of the pubic bone to the top of the uterus. Measuring the fundal height gives the practitioner a better idea of how your baby is growing and whether its size is on track as your pregnancy progresses.

While it is common for a fundal height measurement to be off by a couple of centimeters, a greater discrepancy may warrant a closer look to determine if the fetus is growing normally for its gestational age. If the fundal height is smaller than expected, the fetus may have IUGR. It is sometimes also referred to as fetal growth restriction or small for gestational age (SGA).

Here, we'll take a closer look at intrauterine growth restriction (IUGR), including the causes, what to expect, and how the condition is treated.

Causes of Intrauterine Growth Restriction

Most commonly, IUGR occurs when a growing fetus does not receive enough nutrients and nourishment, typically from issues with the placenta or blood flow in the umbilical cord. A fetus with IUGR usually weighs less than 9 out of 10 babies of the same gestational age.

Some medical conditions in the gestational parent may cause IUGR. These include:

  • Kidney disease
  • Advanced diabetes
  • Heart or respiratory disease
  • Malnutrition or anemia
  • High blood pressure or pregnancy-induced hypertension (PIH)
  • Alcohol or drug use during pregnancy
  • Smoking cigarettes during pregnancy

Intrauterine growth restriction is also possible with placental abruption or placenta previa, an infection in the tissues surrounding the fetus, or chromosomal abnormalities in the fetus.

Symmetric vs. Asymmetric IUGR

There are two main types of intrauterine growth restriction: symmetric (primary) and asymmetric (secondary). There are a few key differences between these.

Symmetric IUGR is typically discovered earlier on during pregnancy and is commonly linked to an infection or genetic disorder. It results in all internal organs of a fetus being reduced in size, and it accounts for 20% to 30% of all IUGR cases. The prognosis is often poor.

With asymmetric IUGR, which occurs in 70% to 80% of cases, the head and brain are normal in size, but the abdomen is smaller. This is typically found later on in pregnancy, during the third trimester. These babies may have complications, but overall their prognosis is good and they usually grow into an age-appropriate size.

Possible Effects of IUGR

Low birth weight comes with a greater risk for many issues, including breathing problems, brain bleeding, jaundice, and infection. While not all complications are serious, some may require a stay in the neonatal care nursery (NICU).

Long-term effects of IUGR are also possible, including heart disease, diabetes, high blood pressure, developmental disabilities, metabolic syndrome, and obesity.

Can You Prevent Intrauterine Growth Restriction?

Intrauterine growth restriction can happen during any pregnancy. That said, there are certain factors that increase risk, such as drug or alcohol use, smoking, or taking certain medications. A healthy diet and appropriate weight gain are also important to ensure a healthy pregnancy and a reduced risk of IUGR.

The best way to monitor your baby's health and risk of IUGR is to keep all your prenatal appointments. Although a diagnosis may be out of your control, regular prenatal care will mean prompt treatment.

Diagnosing Intrauterine Growth Restriction

Intrauterine growth restriction is typically discovered during routine prenatal care. It can be found when your doctor or midwife measures your growing uterus. A size discrepancy of greater than two weeks indicates the need for further investigation.

That will usually mean either:

  • Fetal ultrasound: A technician uses images from an ultrasound to measure the baby, and a diagnosis is based on your baby's measurements compared to its gestational age.
  • Doppler ultrasound: This special type of ultrasound checks the blood flow to the placenta and through the umbilical cord to the baby. A decreased blood flow may indicate IUGR.

Treatment for IUGR

Treatment depends on your baby's gestational age. After 34 weeks, the best option may be to induce labor early. Prior to that, your provider will continue to monitor your baby's growth, amniotic fluid levels, and overall well-being. Your prenatal appointments may become more frequent, and depending on your baby's condition, a premature delivery might be necessary.

If you have a specific condition that is causing IUGR, such as diabetes, your provider will treat that condition. They will also suggest ways to make sure you are staying healthy, eating a nutritious diet, and gaining the appropriate amount of weight.

If your baby is determined to have a growth issue, you may receive more frequent monitoring. This may mean more frequent prenatal visits and testing, such as ultrasounds or non-stress tests. Your practitioner may also recommend bed rest.

A Word From Verywell

If you are worried about the size of your growing baby, the most important thing you can do is prioritize your health and keep up with routine prenatal appointments. If your fundal height measurements seem a little on the small side, try not to worry—your practitioner will determine if a closer look is necessary. They will also take every step required to ensure the best treatment to keep you and your baby safe. 

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4 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Sharma D, Shastri S, Sharma P. Intrauterine growth restriction: Antenatal and postnatal aspects. Clin Med Insights Pediatr. 2016;10:67-83. doi:10.4137/CMPed.S40070

  2. Stanford Medicine Children's Health. Fetal growth restriction.

  3. Columbia University Irving Medical Center. Intrauterine growth restriction (fetal growth abnormality).

  4. March of Dimes. Low birthweight.

By Robin Elise Weiss, PhD, MPH
Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor.