What Is Intrauterine Growth Restriction (IUGR)?

Intrauterine growth restriction, or IUGR, is when a baby in the womb (a fetus) does not grow as expected. The baby is not as big as would be expected for the stage of the mother's pregnancy. This timing is known as an unborn baby's "gestational age."

The two types of IUGR are:

  • symmetrical IUGR: all parts of the baby's body are similarly small in size
  • asymmetrical IUGR: the baby's head and brain are the expected size, but the rest of the baby's body is small

What Causes IUGR?

Often, IUGR happens because the fetus doesn't get enough nutrients and nourishment. This can happen if there is a problem with:

  • the placenta, the tissue that brings nutrients and oxygen to the developing baby
  • the blood flow in the umbilical cord, which connects the baby to the placenta

Intrauterine growth restriction also can happen if a pregnant woman:

How Is IUGR Diagnosed?

Before babies are born, doctors check their growth by measuring the mother's belly from the top of the pubic bone to the top of the uterus. This is called the uterine fundal height.

They also can do a prenatal ultrasound, which is how IUGR often is diagnosed. A technician coats the woman's belly with a gel and then moves a probe (wand-like instrument) over it. High-frequency sound waves create pictures of the baby on a computer screen. These pictures help doctors estimate the baby's size and weight. These estimates aren't exact, but they do help health care providers track the baby's growth and see if there's a problem. Ultrasounds also can help find other issues, such as problems with the placenta or a low level of amniotic fluid (the fluid surrounding the fetus). Doctors will also use ultrasounds to check the blood flow to the placenta and through the umbilical cord.

If they think a baby has IUGR, doctors also might do such tests as:

  • fetal monitoring to track the baby's heart rate and movements
  • screening the mother for infections that could affect the baby
  • amniocentesis to look for genetic causes of IUGR (and sometimes to help them see how mature the baby's lungs are) 

How Is IUGR Treated?

Treatment for intrauterine growth restriction depends on how far along the pregnancy is and how the baby is doing. Doctors will watch a baby with IUGR closely during prenatal visits. They'll do ultrasounds, keep track of growth, and watch for other problems.

If the baby's mother has a condition, doctors will help her manage it. This might include making sure she eats a healthy and nutritious diet and gains the right amount of weight during her pregnancy. Some women might go on bed rest to try to improve blood flow to the baby.

Sometimes, doctors will recommend inducing labor and delivery early. They might do this if the baby seems to have stopped growing, or if there's a problem with the placenta or the blood flow in the umbilical cord.

A woman might have a cesarean section (C-section) if the stress of a vaginal delivery is considered too risky for the baby.

What Problems Can Happen?

Babies with IUGR are more at risk for some kinds of health problems. Those born early or who are very small at birth are more likely to need to stay in the hospital for a longer time. They also might need special care in the neonatal intensive care unit (the NICU).

Other problems that can be related to intrauterine growth restriction include:

  • problems with breathing and feeding
  • trouble keeping a steady body temperature
  • abnormal blood cell counts
  • low blood sugar level (hypoglycemia)
  • problems fighting off infections
  • neurological problems

The long-term effects of IUGR on a baby may depend on the condition that caused the problem.

What Can I Do if My Baby Has IUGR?

If your baby might have IUGR, follow your doctor's advice and go to all prenatal visits and testing appointments. This helps your doctor see how your baby is developing and growing.

Take good care of yourself by:

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.