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

In France, the average weight of a full-term baby is about 3kg to 3.5kg. However, some babies are born with much smaller sizes, particularly those born with Intrauterine Growth Restriction (IUGR), which occurs in 3 to 10% of pregnancies.

What Causes IUGR? A fetus is considered to have IUGR when its measurements fall below the 10th percentile. It is referred to as "severe IUGR" when the fetus is smaller than 3% of fetuses at the same gestational age (below the 3rd percentile). There are several causes of intrauterine growth restriction:

• Placental dysfunction, such as improper positioning or implantation.
• IUGR can also result from a viral illness in the mother or chromosomal abnormalities.
• Exposure to toxins (especially smoking or alcohol consumption during pregnancy) is a common cause.
• Maternal malnutrition (severe vitamin and mineral deficiencies) can also cause IUGR. However, in one-third of cases, no specific cause is found, so it’s important to perform a complete assessment for the mother, including an amniocentesis.

How is IUGR Diagnosed? IUGR is often suspected during the 4th-month exam, when measuring the uterine height. However, the condition is typically confirmed during the 2nd and/or 3rd trimester ultrasound, where measurements of the cranial circumference, femur length, and abdominal circumference of the fetus are taken. These three measurements are used to determine if the baby has IUGR, especially if there is a "break" in the fetus' measurements between the two ultrasounds.

How Does Pregnancy Progress with IUGR? IUGR can be caused by a lack of oxygen supply from the placenta, which can affect the functioning of the baby’s vital organs (especially towards the end of the pregnancy), increasing the risk of fetal death in utero. To minimize this risk, the baby is often delivered prematurely through induction or cesarean section. The mother is placed under intensive monitoring to determine the best time for delivery: not too early to limit risks associated with prematurity, but not too late to minimize those linked to IUGR.

What Are the Consequences of IUGR on the Baby? Babies born with growth restriction are usually "hypotrophic," meaning they are smaller in weight and are therefore more fragile. When a baby is born weighing between 2kg and 2.5kg, the risks of complications are relatively low. However, if the baby weighs below 2kg, closer monitoring is necessary to avoid dehydration, hypoglycemia, or infections.