Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) is a serious condition in which the fetus fails to grow at a normal rate during pregnancy, causing the baby to be smaller than expected for the gestational age (number of weeks in the pregnancy).

A fetus with IUGR generally has an estimated weight below the 10th percentile, meaning it weighs less than 90 percent of babies at that gestational age. At birth, these newborns may be described as small for gestational age (SGA).

IUGR affects the overall size of the baby’s body as well as the growth of the fetal organs, tissues and cells.

The condition is also referred to as fetal growth restriction (FGR).

How does IUGR affect my baby?

Babies with IUGR are at risk of a wide range of complications during pregnancy, delivery, and after birth. In general, the lower the baby’s weight, the greater the risks.  

Risks include:

• Low oxygen levels in the womb caused by lack of blood flow through the placenta, decreasing the fetal heart rate
• Preterm delivery
• Deprivation of oxygen during birth (perinatal asphyxia) affecting the brain and other organs
• Hypothermia (low body temperature due to low body fat)
• Difficulty breathing caused by immature lungs when born prematurelyInability to fight infections
• Difficulty feeding and gaining weight
• Jaundice
• Neurological issues
• Gastrointestinal issues
• Long-term growth problems
• Stillbirth

Types of IUGR

There are two types of IUGR:

• Symmetrical IUGR, where all parts of the baby’s body are smaller than expected (proportionally small)
• Asymmetrical IUGR, where one or more parts of the baby is normal size but the rest of the baby’s body is smaller than expected.

Cause and Risk Factors

Intrauterine growth restriction occurs in an estimated 5 percent of pregnancies. The condition can be caused by maternal, fetal, placental or genetic problems.

Possible causes and risk factors include:

• Placental insufficiency (placenta is unable to deliver adequate oxygen and nutrients to the baby)
• Infections passed from the mother, such as cytomegalovirus (CMV), German measles (rubella), toxoplasmosis and syphilis
• Chronic maternal conditions, including cardiovascular disease, diabetes, hypertension (high blood pressure), lung and kidney disease, and autoimmune diseases.
• Malnutrition or maternal weight less than 100 pounds
• Birth defects, genetic disorders or chromosomal abnormalities
• Living in high altitudes
• Smoking, alcohol or drug use during pregnancy
• Certain medications during pregnancy
• Multiples pregnancy
• Oligohydramnios (too little amniotic fluid)
• History of pregnancies and births with IUGR and SGA

Diagnosis

IUGR is typically diagnosed during a routine ultrasound exam.

Using detailed imaging, measurements are taken of the fetal head, abdomen, arms and legs. Those measurements are then used to calculate the estimated fetal weight and compare it to other babies at the same gestational age. IUGR is usually diagnosed if the fetus has an estimated weight below the 10th percentile.

Additional tools to diagnose IUGR include:

• Fundal height, a measurement of the distance from the top of the pubic bone to the height of the top of the uterus. After 20 weeks, this measurement should closely align with the number of weeks of pregnancy (for example, approximately 34 centimeters fundal height at 34 weeks’ gestation)
• Maternal weight gain

If IUGR is diagnosed, you may be referred to a fetal center for a comprehensive evaluation and specialized care. 

Specialized Evaluation and Additional Testing

At Texas Children’s Fetal Center, we arrange for you to visit as quickly as possible to meet with a team of specialists experienced in diagnosing and treating IUGR, including maternal-fetal medicine (MFM) physicians, fetal imaging experts, genetic counselors and neonatologists.

Additional testing may include:

• High-resolution anatomy ultrasound to confirm the diagnosis, evaluate the condition and identify any birth defects
• MRI for a more detailed view of fetal anatomy, if structural abnormalities are detected
• Fetal echocardiogram to evaluate heart structure and function
• Amniocentesis and chromosomal analysis to screen for genetic abnormalities

Following this detailed assessment, our specialists will meet with you about the results, answer any questions you have, and discuss treatment recommendations. A diagnosis during pregnancy of any underlying fetal birth defects enables your family and your healthcare team to plan ahead for the special needs of your baby at birth and arrange for the earliest possible treatment.

Treatment During Pregnancy

You and your baby will be closely monitored throughout pregnancy to watch for signs of complications. Testing may include:

• More frequent ultrasounds to assess fetal growth
• “Nonstress” tests to monitor fetal activity and heart rate
• Doppler ultrasound to evaluate fetal circulation

Treatment strategies during pregnancy include:

• Management of maternal health issues, such as diabetes or high blood pressure
• Good nutrition for weight gain
• Hospitalization, if needed, to manage complications and prevent premature birth
• Management of any underlying birth defects or genetic abnormalities and preparations for advanced care and treatment at birth, to optimize fetal outcomes
• Early delivery, if needed, for the health and safety of you and your baby

Delivery

Babies with IUGR are at risk of oxygen deprivation during the birth process. We recommend delivery at a hospital with the expertise and resources required to treat these potentially life-threatening deliveries, including the highest level of neonatal intensive care (NICU) for premature and critically ill newborns. A cesarean delivery may be required if the baby’s health deteriorates during labor and delivery.

Delivery and postnatal care should be carefully planned and coordinated with a team of maternal-fetal medicine specialists, neonatologists, and pediatric specialists experienced in working together to treat IUGR complications and any associated birth defects, ensuring the best possible care beginning at birth.

Our Fetal Center team works closely with pediatric experts from Texas Children’s Hospital, consistently ranked one of the best children’s hospitals in the nation by U.S. News & World Report, meeting your baby’s every need, every step of the way.

Treatment After Birth

Treatment at birth varies depending on the cause of IUGR, including the presence of any associated birth defects or genetic conditions, and the gestational age at delivery.

In severe cases, IUGR babies may require lengthy stays in the NICU and the highest level of respiratory support. Surgery may be required to repair a congenital abnormality.  

Postnatal Care Team

A unique and distinct advantage for mothers delivering at Texas Children’s Pavilion for Women is our location inside one of the largest and most renowned children’s hospitals in the world, for seamless access to the critical care services and specialists your child may need.

For babies with IUGR, this means no transfers during critical postnatal periods. It also means that the pediatric experts responsible for treating your child have been an integral part of their care team since before birth.

Your baby’s postnatal care team may include:

• Neonatologist
• Pulmonologist
• Cardiologist
• Neurologist
• Gastroenterologist
• Pediatric surgeon

Texas Children’s is ranked number one in the nation in pediatric cardiology and heart surgery, number one in pulmonary care, number two in gastroenterology, and number three in neurology and neurosurgery by U.S. News and World Report. Six of the hospital’s subspecialties rank in the top three and all rank in the top 10.  

Why Texas Children’s Fetal Center?

• A single location for expert maternal, fetal and pediatric care. At Texas Children’s Hospital, mother and baby can get the specialized care required for the diagnosis and treatment of IUGR, and any related fetal anomalies, all in one location, including immediate access to our level IV NICU, avoiding the need to transport your critically ill newborn.
• A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine physicians, fetal imaging specialists, neonatologists, genetic counselors, and others who work in concert to care for you and your baby every step of the way, using protocols we’ve developed over the years. With their combined expertise and unified approach, these physicians offer the best possible care for babies with IUGR.
• We care for your child’s needs at every stage of life. Our comprehensive approach starts with your first prenatal visit for IUGR and continues through your child’s delivery, postnatal care, and throughout childhood, when needed, thanks to one of the nation’s leading teams of fetal and pediatric specialists for the treatment of rare fetal conditions and birth defects.