What is fetal growth restriction (FGR)?

Fetal growth restriction (FGR) is a condition in which an unborn baby (fetus) is smaller than expected for the number of weeks of pregnancy (gestational age). It's often described as an estimated weight less than the 10th percentile. This means that the baby weighs less than 9 out of 10 babies of the same gestational age. Newborn babies with FGR may be called “small for gestational age.”

FGR can begin at any time during pregnancy. With FGR, the baby doesn't grow well. FGR may affect the overall size of the baby and the growth of organs, tissues, and cells. This can cause many problems. But many newborns who are small may just be small. They may not have any problems.

What causes FGR?

Many things increase the risk for FGR. These include problems with the placenta or umbilical cord. The placenta may not attach well. Or the blood flow through the umbilical cord may be limited. Factors in both the mother and the baby may cause FGR.

Factors in the mother that can cause FGR include:

• High blood pressure or other heart and blood vessel disease

• Diabetes

• Too few red blood cells (anemia)

• Long-term lung or kidney conditions

• Autoimmune conditions, such as lupus

• Very low weight

• A large amount of excess weight (obese)

• Poor nutrition or weight gain

• Alcohol or drug use

• Cigarette smoking

Factors in the baby that can cause FGR include:

• Being one of a twin or triplets

• Infections

• Birth defects, such as heart defects

• Problem with genes or chromosomes

What are the symptoms of FGR?

A pregnant woman doesn’t have symptoms of FGR. But a baby with FGR may have certain signs after birth, such as:

• Low birth weight

• Low blood sugar levels

• Lower body temperature

• High level of red blood cells

• Trouble fighting infections

How is FGR diagnosed?

One of the main reasons for regular prenatal exams is to make sure your baby is growing well. During pregnancy, the size of your baby is estimated in different ways, including:

• Fundal height. To check fundal height, your healthcare provider measures from the top of your pubic bone to the top of your uterus (fundus). Fundal height, measured in centimeters (cm), is about the same as the number of weeks of pregnancy after the 20th week. For example, at 24 weeks gestation, your fundal height should be close to 24 cm. If the fundal height is less than expected, it may mean FGR.

If your healthcare provider thinks you have FGR, you'll have other tests. These include: 

• Fetal ultrasound. Estimating fetal weight with ultrasound is the best way to find FGR. Ultrasound uses sound waves to create images of the baby in the uterus. Sound waves won't harm you or the baby. Your healthcare provider or a technician will use the images to measure the baby. A diagnosis of FGR is based on the difference between actual and expected measurements at a certain gestational age.

• Doppler ultrasound. You may also have this special type of ultrasound to diagnose FGR. Doppler ultrasound checks the blood flow to the placenta and through the umbilical cord to the baby. Decreased blood flow may mean your baby has FGR.

You may have repeat ultrasound exams, Doppler studies, and other tests.

How is FGR managed?

Management depends on how serious the FGR is. This is based on the ultrasound (estimated fetal weight) and Doppler ultrasound (blood flow to the baby), as well as risk factors and the number of weeks gestation.

Treatment may include:

• Frequent monitoring. This means you will have prenatal visits more often, and ultrasound and Doppler ultrasound exams. You may have other tests.

• Tracking fetal movements. Your healthcare provider may also ask you to keep track of fetal movements. If so, they will give you instructions.

• Corticosteroid medicine. This medicine may be given to you to help mature the baby's lungs, as well as other organs.

• Hospital stay. You may have to remain in the hospital so the baby can be watched closely.

• Early delivery or emergency cesarean section

What are possible complications of FGR?

FGR can cause many serious complications. Your baby may need to be delivered early and stay in the hospital. Your baby may have trouble breathing, infections, and other problems. Stillbirths and death may occur. As your child grows, they'll be at higher risk for heart and blood vessel problems.

How can FGR be prevented?

FGR can happen in any pregnancy. But some factors, like cigarette smoking or alcohol or medicine use, increase the risk for FGR. Regular and early prenatal care and a healthy diet and steady weight gain help to prevent FGR and other problems.

When should I call my healthcare provider?

Make sure your healthcare provider knows your health history. If you're counting fetal movements and find that the number has decreased, let your healthcare provider know. And if you notice other changes or if you have concerns about your pregnancy, call your healthcare provider.

Key points about fetal growth restriction

• FGR is a condition in which the baby is smaller than expected for gestational age.  

• Many factors increase the risk for FGR. They may be related to the placenta, mother, or baby.

• Estimating fetal weight with ultrasound is the best way to identify FGR.

• If FGR is diagnosed, you will need to be closely watched.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions, especially after office hours or on weekends.