Definition

Intrauterine Growth Restriction (IUGR) is a condition where the fetus is smaller than expected for its gestational age. This means that the rate of fetal growth in the womb is not as expected. Compared to other babies, the fetus has a weight that is less than 9 out of 10 babies of the same age.

IUGR may begin at any time during pregnancy and occurs in about 10% of all pregnancies. A smaller fetal growth can affect the baby's body size and the development of its organs and tissues, potentially leading to problems before and after birth.

However, it is important to note that fetal growth rates in the womb can vary. Even though a fetus is small, it doesn't necessarily mean there are health issues. Just like adults who are shorter in stature, it doesn't mean they are less healthy than taller individuals.

There are two types of IUGR:

1. Primary IUGR (30% of all cases), where the entire body of the fetus is small.
2. Secondary IUGR (70-80% of all cases), where only the abdomen of the fetus is small, while the size of the head and brain is consistent with the gestational age.

Causes

There are several possible causes of IUGR, both related to the mother and the fetus. Sometimes the exact cause of IUGR is not identified.

Generally, this condition occurs due to issues with the placenta or umbilical cord. These tissues are essential for delivering nutrients, oxygen, and blood to the fetus. The placenta might not be properly attached to the uterus, or blood flow to the placenta may be restricted. Without adequate nutrition, the fetus can be smaller than expected for its gestational age.

In twin pregnancies, babies are usually smaller than usual. IUGR can affect up to 25% of twin pregnancies. Twins sharing a placenta may experience an imbalance in blood and nutrient flow, causing one baby to be significantly smaller than the other. Fetuses sharing one amniotic sac may also be at risk if the umbilical cords become entangled or twisted, reducing blood flow.

Additionally, you can read our article about twin pregnancy here: Twin Pregnancy - Definition, Cause And Risk Factor.

Risk Factor

Several maternal and fetal factors can contribute to restricted fetal growth in the womb.

Maternal factors that can increase the risk of IUGR include:

• Currently experiencing a twin pregnancy
• A history of a previous pregnancy with IUGR
• Smoking, alcohol consumption, or drug abuse
• Living at high altitudes above 5,000 feet
• Very low or excessive maternal weight (obesity)
• Having medical conditions such as:
• High blood pressure
• Heart disease
• Anemia or a deficiency of red blood cells in the body
• Autoimmune diseases (conditions where the immune system attacks healthy body cells) such as lupus
• Chronic kidney or lung disease
• Diabetes melitus
• Consuming anti-seizure medications
• Pregnancy-related infections

Fetal factors that can increase the risk of IUGR include:

• Genetic or chromosomal abnormalities, such as Down syndrome
• Developmental issues with organs, such as congenital heart defects
• Fetal infection

Toxoplasmosis is one infection that can affect a fetus. The article is available here: Congenital Toxoplasmosis - Definition, Cause And Risk Factor.

Symptoms

Most mothers do not experience any symptoms or signs indicating that their fetus is small for its gestational age. If this is not the first pregnancy, you may notice that your belly is not as large as it should be. Only a doctor can assess whether the fetus or baby is experiencing growth restriction.

The main indicator is that the fetus is small for its gestational age. When the baby is born, the following signs may be observed:

• The baby is small and appears pale
• Low blood sugar levels
• Low body temperature
• The baby is easily sick and has difficulty fighting against infections

Diagnosis

During pregnancy, routine prenatal checkups are recommended. At these check-ups, your weight will be measured, and the height of your uterus will be assessed. The doctor will also perform a physical examination by palpating the mother's abdomen. From this examination, the doctor can estimate the fetus's position, size, and whether there are twins.

Share any complaints you experience during pregnancy with your doctor. As pregnancy progresses, the fetus's heartbeat will also be checked. If insufficient maternal weight gain and a shorter-than-expected uterus height are observed, additional tests such as an ultrasound (USG) may be recommended.

On an ultrasound, imaging can help measure the fetus and monitor its growth, as well as identify whether there is a twin pregnancy. The doctor may also use an ultrasound to check blood flow from the placenta through the umbilical cord (Doppler flow). Poor blood circulation may indicate IUGR. Additionally, the ultrasound can measure the amount of amniotic fluid surrounding the fetus. Low amniotic fluid levels may indicate IUGR.

Management

Generally, if you do not have risk factors related to pregnancy and your fetus is healthy, the pregnancy will be monitored more closely. The doctor will monitor the fetus to ensure there are no complications. Treatment will be provided if the mother or fetus has a medical condition contributing to IUGR.

As pregnancy progresses, the fetus's heartbeat and movements will also be monitored. You should observe the fetus's movements daily, noting whether the fetus is actively moving or starting to become less active. A significant decrease in fetal movements can be a warning sign requiring immediate attention.

Most IUGR babies will reach normal child size by the age of 3. It is important to know that each child grows differently, and you should not overfeed your child. Your pediatrician will determine the next steps if they feel your baby's growth is not progressing as expected.

Complications

Several conditions and problems associated with IUGR include:

• Increased risk of cesarean delivery and preterm birth
• Respiratory and feeding difficulties at birth
• Lack of oxygen at birth
• Low blood sugar levels at birth
• Meconium aspiration or inhalation of the first stool
• Polycythemia (increased red blood cell count in the body)
• Increased susceptibility to infections

Some babies born prematurely (before 36 weeks of gestation) or small may require special care in the hospital.

Prevention

Several factors that can help reduce the risk of IUGR include:

• Avoiding drugs and alcohol
• Quitting smoking
• Maintaining a healthy diet so that weight gain is appropriate for gestational age
• If you have certain medical conditions, regularly monitor your pregnancy to ensure that your condition does not pose a risk to you or the baby

When to See a Doctor?

Confirm that your doctor has been informed about your medical history. If you notice that fetal movements are decreasing, inform your doctor immediately. If you notice any other changes or have concerns about your pregnancy, consult your doctor.

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