What is intrauterine growth restriction (IUGR)?

Intrauterine growth restriction (IUGR) (also referred to as fetal growth restriction, or FGR) describes a condition in which the unborn baby is smaller than expected for his or her gestational age, or the number of weeks that the baby has been in the uterus. The term for a newborn baby who is smaller than expected is small for gestational age (SGA).

Unborn babies with IUGR typically have an estimated weight that is less than the 10th percentile. That means their weight falls below that of 90 percent of unborn babies of the same gestational age. They may be proportionally small (all parts of the baby are smaller than expected) or asymmetrically small (one part of the baby is smaller than expected). IUGR babies are sometimes born prematurely (before 37 weeks of pregnancy).

Babies with IUGR are at greater-than-normal risk for a variety of health problems before, during and after their birth. These problems include low oxygen levels while in the womb, a high level of distress during labor and delivery, and an increased risk of infectious disease after birth. IUGR also raises the risk of long-term growth problems and metabolic disease (a group of health problems that put children at risk of chronic diseases, such as type 2 diabetes and heart disease).

Not all babies whose weight is in the 10th percentile have complications or concerns related to IUGR, however. Many healthy babies are born small due to their parents being smaller than average in stature.

Who will be on my care team?

At Midwest Fetal Care Center, a collaboration between Children’s Minnesota and Allina Health, we specialize in individual attention that starts with you having your own personal care coordinator to help you navigate the complex process of caring for your babies. We use a comprehensive team approach to IUGR. That way, you are assured of getting the best possible information by some of the most experienced physicians in the country. For IUGR, your care team may include a maternal-fetal specialist, a pediatric cardiologist, a neonatologist, a nurse specialist care coordinator, a perinatal social worker and several other technical specialists. This entire team will follow you and your baby closely through the evaluation process, and the team will be responsible for designing and carrying out your complete care plan.

Meet the team

What causes intrauterine growth restriction (IUGR)?

The restricted growth associated with IUGR is caused by the baby not receiving enough nutrients and oxygen in the uterus to grow at a normal rate. Many factors can lead to an insufficient flow of nutrients and oxygen. As shown in the lists below, possible factors fall into three main categories: some are related to the mother, others to the baby and still others to abnormalities in the placenta and/or uterus.

  • Maternal-related factors: a chronic disease that affects the mother’s heart, lungs, kidneys, liver, or blood, such as high blood pressure, severe diabetes or an autoimmune disease; cigarette smoking or other substance abuse; exposure to particular medications (such as certain anticonvulsants); infections that can get passed on to the baby (such as cytomegalovirus or rubella)
  • Baby-related factors: birth defects; chromosome or genetic abnormalities; infections; being part of a multiple birth, such as twins or triplets
  • Placenta/uterine-related factors: small placental size; abnormal blood flow through the placenta; large uterine fibroids behind the placenta; placental masses (benign tumors consisting of abnormal grouping of blood vessels); an abnormal insertion of the umbilical cord into the placenta; placental abruption (an area of the placenta that separates from the uterus); an abnormally shaped uterus

How is intrauterine growth restriction (IUGR) diagnosed?

IUGR may develop at any time during pregnancy. The key tool used to diagnosis the condition is ultrasound. Ultrasound enables your doctor to accurately measure the size of your baby’s head, abdomen, arms and legs. Those measurements are then used to calculate the baby’s estimated weight, which is compared with a growth chart of the average weight of babies at a similar gestational age.

Starting at around 20 weeks, your doctor will estimate the size of your baby at each prenatal visit. Your doctor will do this by measuring the distance from the mother’s pubic bone to the height of the top of the uterus (the fundus). If the measurement is not as expected for the number of weeks of the pregnancy, or if the mother has had difficulty gaining weight, an ultrasound will be ordered to determine if your baby has IUGR.

If you are at high risk of having a baby with IUGR, your doctor will follow your baby’s growth during the pregnancy with early and more-frequent-than-usual ultrasound exams.

Once IUGR is diagnosed, other tests may be conducted to try to determine the cause of the condition. If it’s thought that the cause may be a maternal infection, for example, a sample of the mother’s blood may be taken and tested for signs of a recent infection. In some cases, an amniocentesis test, which can be used to evaluate amniotic fluid for signs of infection, may be recommended.

To determine if the IUGR is related to a genetic abnormality, the ultrasound images of your baby’s anatomy will be carefully examined for signs of birth defects. You may be referred to a genetic counselor, who will discuss options for genetic testing.

Ultrasound images are also used to determine if there is too little amniotic fluid around the baby (a condition known as oligohydramnios) or if there is an abnormal flow of blood from the umbilical cord into the placenta. Both are associated with the development of IUGR. A special type of ultrasound known as Doppler flow, which measures the speed and amount of blood as it moves through a blood vessel, may be used to assess how the baby is responding internally to the growth restriction.

The rate of your baby’s growth (how much the baby grows between your prenatal visits) will be closely followed. This monitoring often helps to distinguish between a baby who is smaller-than-average but healthy and one who has IUGR. For example, if the baby’s growth continues to increase between prenatal visits, if the amount of amniotic fluid is normal, and if blood flow into the placenta is normal, then the baby is less likely to have the condition.

How is intrauterine growth restriction (IUGR) managed before birth?

Our prenatal management of babies with IUGR centers on monitoring the baby frequently with high-resolution ultrasonography. To gather additional information, other technologies may be used, including fetal echocardiography and amniocentesis.

What is high-resolution fetal ultrasonography?

High-resolution fetal ultrasonography is a non-invasive test performed by one of our ultrasound specialists. The test uses reflected sound waves to create images of your baby within the womb. We will use ultrasonography to follow the development of your baby’s internal organs and overall growth throughout the pregnancy. The test will also allow us to keep track of the amount of amniotic fluid surrounding your baby, as well as how well blood is flowing through the umbilical cord, as well as within your baby’s other blood vessels.

What is fetal echocardiography?

Fetal echocardiography (“echo” for short) is performed at our center by a pediatric cardiologist (a physician who specializes in fetal heart abnormalities). This non-invasive, high-resolution ultrasound procedure looks specifically at how your baby’s heart is structured and how well it is functioning within the womb.

What is amniocentesis?

An amniocentesis is done to sample the amniotic fluid around your baby. This fluid will contain some of your baby’s cells, which will provide a full set of your baby’s chromosomes for us to analyze. Amniotic fluid can also be assessed for infection if there is suspicion that an infection could be contributing to IUGR. The amniocentesis procedure is straightforward and can be done in our clinic. It requires placing a small needle through the mother’s abdomen and into the amniotic sac to obtain the fluid sample. Getting final results from the test from our laboratory usually takes several days. The information will be very important for creating your care plan and helping the neonatologist care for your infant after birth.

How is intrauterine growth restriction (IUGR) managed before birth?

The prenatal management of IUGR depends on a variety of factors, including the severity of the baby’s growth restriction, the timing of when during the pregnancy the IUGR began, the mother’s health, and the presence of any birth defects or genetic anomalies. Babies with IUGR are at increased risk of stillbirth. To reduce this risk, your baby will be closely monitored.

In addition to frequent ultrasound exams, one or more of the following techniques may be used by your doctor to monitor your pregnancy and watch for potential problems:

Fetal-kick counting. Your doctor may ask you to keep track of your baby’s kicks and movements. If your baby’s movements change significantly, it might be a sign that the baby is under stress.

Non-stress test. For this test, a special monitor is placed on the mother’s abdomen to listen to the baby’s heart-rate pattern. Certain changes in the baby’s heart rate can be a sign that the baby is under stress.

Biophysical profile. This test is a combination of the non-stress test and an ultrasound. A heart-rate monitor is placed on the mother’s abdomen during an ultrasound exam, allowing your doctor to observe the baby’s heart rate while the baby is moving within the womb. Your doctor will use the test, which can last for up to 30 minutes, to determine if your baby is receiving enough oxygen from the placenta. The test also helps to assess the amount of amniotic fluid surrounding the baby.

Doppler flow studies. Doppler flow is a particular type of ultrasound. It uses sound waves to measure the amount and speed of blood as it moves through a blood vessel. Your doctor will use Doppler flow to observe how well blood is flowing to the umbilical cord. The test will also enable your doctor to assess blood flow in your baby’s brain, heart and other organs.

How is intrauterine growth restriction (IUGR) treated before birth?

Sometimes a mother can take steps to improve the growth of her unborn baby, such as by stopping smoking or by eating more nutritious foods. In most cases, however, the mother is unable to affect the growth of the baby. Prenatal treatment for IUGR focuses, therefore, on close monitoring of the pregnancy. The goal is to continue the pregnancy for as long as safely possible.

In some cases, hospitalization of the mother is recommended. This enables the unborn baby to be very closely monitored. If IUGR endangers the health of the baby, an early delivery may be necessary. Babies with IUGR are often delivered by cesarean section, as their weakened condition can make it difficult for them to tolerate the stress of labor and delivery.

How is intrauterine growth restriction (IUGR) treated after birth?

Many babies with IUGR are born prematurely, but our goal will be to have your baby delivered as close to your due date as possible. If early delivery is a concern, we will recommend that your baby be born at a hospital able to care for premature babies, such as The Mother Baby Center at Abbott Northwestern and Children’s Minnesota in Minneapolis or The Mother Baby Center at United and Children’s Minnesota in St. Paul. Children’s Minnesota is one of only a few centers nationwide with a birth center located within the hospital complex. This means that your baby will be born just a few feet down the hall from our newborn intensive care unit (NICU). Also, many of the physicians you have already met will be present during or immediately after your baby’s birth to help care for your baby right away.

What is my baby’s long-term prognosis?

The long-term prognosis for babies with IUGR depends on the severity of the condition, the reason for the IUGR (such as a birth defect), and the age of the baby at delivery. The longer the baby stays in the womb before birth, the less likely he or she will experience complications.

Some of the health problems babies with IUGR may experience after birth are low blood sugar, difficulty maintaining normal body temperature, difficulty eating and neurodevelopmental delays.

Will my baby require long-term follow-up?

Because of the potential health issues associated with IUGR, your baby may require long-term follow-up care. At Children’s Minnesota, we have developed a detailed care plan for babies who experienced IUGR during pregnancy. Your baby’s plan will be implemented by a comprehensive team of specialists, including a pediatrician (who will coordinate your baby’s overall care), a pediatric cardiologist, a developmental specialist and any other caregiver your baby may require.

Contact us

Need a referral or more information? You or your provider can reach the Midwest Fetal Care Center at 855-693-3825.