Fetal Growth Restriction (FGR)
What is fetal growth restriction (FGR)?
Fetal growth restriction (FGR) is when the fetus is smaller than expected for the number of weeks of pregnancy. Another term for FGR is intrauterine growth restriction (IUGR). Newborn babies with FGR are often described as small for gestational age.
A fetus with FGR often has an estimated fetal weight less than the 10th percentile. This means that the fetus weighs less than 90% of all other fetuses of the same gestational age. A fetus with FGR may be born at term (after 37 weeks of pregnancy) or prematurely (before 37 weeks).
Newborn babies with FGR 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 fetal growth restriction (FGR)?
Fetal 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 get the needed 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 FGR is due to other causes. Some factors that may contribute to FGR include the following:
Why is fetal growth restriction (FGR) a concern?
FGR can begin at any time in pregnancy. Early-onset FGR 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 FGR, 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 FGR 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 FGR may result in stillbirth. It may also lead to long-term growth problems in babies and children.
How is fetal growth restriction (FGR) 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 FGR.
Other tests 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 FGR 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 fetal growth restriction (FGR) managed?
Management of FGR 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 FGR 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 FGR
Your baby's health care provider will figure out the best treatment for your baby based on:
How old your baby is
His or her overall health and medical history
How sick he or she is
How well your baby can handle specific medications, procedures, or therapies
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 FGR endangers the health of the fetus, then an early delivery may be needed.
Prevention of fetal growth restriction
Fetal growth restriction may occur, even when the mother is in good health. However, some factors may increase the risks of FGR, 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 FGR. Early detection may also help with FGR treatment and outcome.
- MMI board-certified, academically affiliated clinician
- Trevino, Healther, M., BSN, RNC