baby growth IUGR

Everything You Need to Know About IUGR (Intrauterine Growth Restriction)

Throughout your pregnancy, your doctor will monitor the growth of your baby at every appointment. The doctor may measure the size of your bump using a tape measure (fundal height measurement), or may measure the size of your baby during an ultrasound test.

This is to make sure that your baby is growing at the correct rate. If your doctor thinks your baby is growing too slowly, they may diagnose your baby with IUGR.

What is IUGR?

IUGR (intrauterine growth restriction) is the name given to describe cases where an unborn baby is growing more slowly than expected. The baby will be smaller in size than normal for its gender and week of pregnancy.

How many types of IUGR are there?

There are two types of IUGR: symmetrical IUGR and asymmetrical IUGR.

1. Symmetrical IUGR:

When a baby has developed slowly from the beginning of the pregnancy, his whole body will be smaller than expected. The size of his head will be in proportion to his body.

This is called Symmetrical IUGR, and is sometimes referred to as Global Growth Restriction.

2. Asymmetrical IUGR:

Asymmetrical IUGR is when some parts of the baby’s body are smaller in proportion to others. This is usually the case when a baby has developed normally throughout the pregnancy, but has begun to experience growth restriction during the third trimester.

In this case, the baby will prioritise the growth of its head and brain, while the abdomen will continue to grow at a slower rate.

Babies with asymmetrical IUGR have heads that are bigger in proportion to the rest of their body.

What causes IUGR?

IUGR can be caused by a number of reasons, and in many cases, the exact cause is unknown.

Symmetrical IUGR is usually caused by problems related to the fetus, such as a chromosomal abnormality, or an infection that is transmitted from the mother to the baby during early pregnancy.

In cases of asymmetrical IUGR, the growth restriction is usually caused by a problem with the uterus or the mother that prevents the baby from receiving enough nutrients or oxygen to grow.

There are a number of factors that may increase the risk of IUGR:

Maternal risk factors:

  • Malnutrition
  • Being underweight before pregnancy
  •  Insufficient weight gain during pregnancy
  •  The use of drugs
  •  The use of alcohol
  •  Smoking
  •  High blood pressure
  •  Celiac disease
  •  Anaemia
  •  Diabetes before pregnancy
  •  Gestational diabetes (diabetes that begins during pregnancy)
  •  Heart disease
  •  Respiratory disease
  •  Renal disease

Uterus and placental risk factors:

  • Being pregnant with multiple babies
  •  Pre-eclampsia
  •  Placental insufficiency (the placenta can’t deliver sufficient nutrients or oxygen to the baby)
  •  A malformed uterus

Fetal risk factors:

  • Chromosomal abnormalities such as Down Syndrome, Edwards Syndrome, and Patau Syndrome
  • Birth defects.
  •  Infections transmitted from the mother to the baby such as Toxoplasmosis or Rubella.

How do I know if my baby has IUGR?

Many women worry about the size of their bump, and wonder whether their baby is growing well. There is no way to tell whether your baby has IUGR just by looking at your bump. Only your doctor can diagnose your baby with IUGR.

Your doctor may measure the size of your bump by measuring the distance from your pubic bone to the top of your uterus. This is called the fundal height measurement.

If your doctor thinks that your fundal height measurement is too small, she may carry out an ultrasound test to measure the size of your baby’s body.

In many cases, a small fundal height measurement is nothing to worry about. It can be caused by a miscalculation of your due date, or the baby may be sitting in a different position.

During the ultrasound test, your doctor will measure the size of your babies head, abdomen and legs.

These measurements allow your doctor to calculate the approximate weight of your baby. Your doctor will compare the weight of your baby to the expected weight for babies of the same gestational age.

If your baby’s weight is lower than the 10th percentile, meaning that the baby weighs less than 90% of babies of the same age, your doctor may diagnose the baby with IUGR.

Your doctor can also diagnose your baby with IUGR if it hasn’t grown as much as expected since the last ultrasound.

What are the risks of IUGR?

A baby with IUGR may not be receiving enough oxygen or nutrients in order to grow. This can lead to complications such as low levels of amniotic fluid or a reduction of the baby’s heart rate.

IUGR can be a serious condition, and many babies with IUGR have problems at birth including low oxygen levels, respiratory distress, low blood sugar and difficulty maintaining body temperature.

IUGR has also been associated with a higher risk of stillbirth, which is why it is important to follow your doctor’s recommendations about your treatment plan in order to reduce the risks associated with IUGR.

How is IUGR treated?

There is often no specific treatment for IUGR, and your doctor may just recommend extra monitoring of your baby, to check that the baby continues to be healthy. If monitoring shows that the baby’s health is at risk, your doctor may decide that it is safer to deliver your baby early.

Depending on the cause of IUGR, some treatments may be possible during pregnancy and labor.

Extra monitoring

  • Kick counts: You will be asked to monitor your baby’s movement throughout the day, and may be told to contact your doctor if you notice a decrease in movement.
  • Extra ultrasound tests: This is to measure the rate of your baby’s growth.
  • NST tests: Non-Stress Tests measures whether your baby’s heartbeat increases when your baby moves, which is a sign that your baby is healthy.
  • Doppler flow study: This test checks the flow of blood in the placenta and umbilical cord.

Treatments that may improve IUGR symptoms:

  • Any maternal illnesses that contribute to IUGR should be treated.
  • You should not use cigarettes, drugs or alcohol.
  • Some doctors may prescribe bed-rest, to increase blood flow to the uterus.
  • Steroids can be administered to increase your baby’s lung maturity in case your doctor decides it is safer to deliver the baby early.
  • Some studies have shown that low-dose aspirin therapy may help in the treatment of IUGR, although this is controversial.

Treatment during labor:

  • Your baby’s heartbeat should be monitored throughout labour.
  • You should give birth in a hospital that has resources to deal with complications that are associated with IUGR.
  • If the doctor is worried about the health of your baby, she may deliver your baby quickly by caesarean section.

What is the long-term prognosis for babies with IUGR?

The long-term prognosis for babies with IUGR depends on the underlying cause of the growth restriction. If the restriction was caused by factors such as a chromosomal abnormality, the baby may experience complications relating to their condition. Babies with asymmetrical IUGR typically do well after birth, and catch up with the weight of their peers within one year of life.

However, studies have shown that IUGR babies may be at an increased risk of developing Type 2 diabetes, abdominal obesity, and hypertension when they grow up.


Additional references:

Militello, M., Pappalardo, E. M., Ermito, S., Dinatale, A., Cavaliere, A., & Carrara, S. (2009). Obstetric management of IUGR. Journal of Prenatal Medicine, 3(1), 6–9.

Peleg D, Kennedy CM, Hunter SK (1998). Intrauterine growth restriction: identification and management. American Family Physician, 1998 Aug; 1;58(2):453-460.

Barker DJ, Hales CN, Fall CH, Osmond C, Phipps K, Clark PM. Type 2 (non-insulin-dependent) diabetes mellitus, hypertension and hyperlipidaemia (syndrome X): relation to reduced fetal growth. Diabetologica. 1993;36:62–7.

Phipps K, Barker DJ, Hales CN, Fall CH, Osmond C, Clark PM. Fetal growth and impaired glucose tolerance in men and women. Diabetologica. 1993;36:225–8.

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