Intrauterine Growth Restriction (IUGR)

What is IUGR?

IUGR stands for intrauterine growth restriction and simply means that the unborn baby has not grown to a size that is expected for a certain stage of pregnancy. In other words the fetus is smaller than expected. The more correct medical definition is a fetal weight below the 10th percentile for gestational age as measured on ultrasound. It is also known as small for gestational age (SGA).

This can occur for any number of reasons and sometimes the baby may appear smaller in size on ultrasound but is actually a normal size when born. It is also possible that some babies are just naturally smaller in size. The problem is when the babies smaller size is due to some impairment while it is growing in the uterus thereby preventing the fetus from growing to its natural size.

Types of IUGR

There are broadly two types of IUGR.

  • Symmetric IUGR means thats the entire body and organs are smaller in size. Therefore the baby’s body is in proportion but smaller than would be expected.
  • Assymetric IUGR is where the head and brain are normal in size but the abdomen and limbs may be smaller than normal. This can occur when the body starts shunting more blood to the head and brain to maintain its normal growth but at the expense of other organs.

Assymetric IUGR is more commonly seen than symmetric IUGR. It may not be a permanent defect and after birth the proportions of different body parts may gradually return to normal. It is difficult to establish assymetric IUGR until the latter half of pregnancy when the baby’s body should be growing proportionally.

Causes of IUGR

There are number of different causes of IUGR. One of the main reasons why it occurs is due to insufficient oxygen supply to the baby. Often this is related to placental problems. The growth of different body parts are dependent on its oxygen supply as much as it is determined by nutrients and hormones. If there is inadequate oxygen then the tissue growth will be restricted to a size that can be sustained by the existing oxygen supply. IUGR is therefore commonly seen in multiple births, like twins or triplets, where the mother’s body cannot cope with the oxygen requirements of the babies.

However, IUGR may also occur for a host of other causes. Sometimes it may arise with a placenta that matures too early for the respective stage of pregnancy. It can also occur in mothers who smoke, drink alcohol or abuse prescription medication or use illicit drugs during pregnancy. IUGR may also arise with chronic hypertension (mother) and preeclampsia. Some genetic defects can also cause IUGR. Severe malnutrition may also contribute to IUGR as well as certain infections such as rubella, syphilis and toxoplasmosis during pregnancy. Women who are underweight prior to falling pregnant may also be at risk.

Treatment of IUGR

There is no specific treatment for IUGR. Mothers are usually advised to eat well and have plenty of bed rest. By reducing the mother’s demand for oxygen through resting, more oxygenated blood can reach the baby. Cigarette smoking and alcohol consumption should be strictly avoided during pregnancy but if the mother is still persisting with these habits, then she has to stop immediately to not further worsen the condition. Depending on the types of prescription medication used, a doctor may decide that it should be discontinued during the pregnancy so as not to affect the fetus. However, prescription medication should not be stopped unless the doctor advises it.


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