One third of low birth weight babies have intrauterine growth retardation. Find out what it is and what the causes are.

That a baby is born with low weight can be due to several causes. One of them is intrauterine growth retardation (IRG). One third of low birth weight babies have had abnormal growth inside the womb. As a consequence, they have not been able to develop normally, and therefore have not managed to reach the size they should.

But you don’t have to wait for birth to realize that intrauterine growth retardation has occurred. The problem is usually detected from the second trimester of pregnancy .

During the second ultrasound, which is usually done between 18 and 20 weeks, the specialist will measure the baby. If the fetus is below the 10th percentile, you will already begin to suspect that it may be due to the CIR and will perform another series of tests. A baby is also considered to be underweight when it weighs less than 2.5 kilos at birth.


A shortage in the amount of amniotic fluid can be an indication. An ultrasound called Doppler is also performed, in which the speed of blood flow in the fetus, umbilical cord, placenta and uterus can be seen.

In case intrauterine growth retardation is confirmed, very frequent controls are carried out and the mother is recommended to rest and follow a diet rich in proteins and calories.


The reasons that can cause retarded intrauterine growth are several. Next, we will list the most common:

  • Placental insufficiency: The baby does not get nutrients well because there is a problem in the placenta or the vessels that join it to the fetus.
  • Abnormalities in the umbilical cord.
  • Genetic causes.
  • Certain diseases of the mother, such as anemia, hypertension or gestational diabetes .
  • Infections contracted during pregnancy.
  • fetal malformations.
  • The monitoring of an inadequate diet by the mother. In this sense, it is important to note that pregnant women who consume less than 1,500 calories a day during the third trimester of pregnancy are more likely to have a baby with RIC.
  • Another risk factor is that the mother weighs less than 45 kilos, measures less than 1.50 cm and does not gain weight during pregnancy.
  • Using alcohol and drugs or smoking during pregnancy. These substances can prevent the baby from getting the oxygen and nutrients needed to develop properly.
  • Make excessive physical efforts.
  • Multiple pregnancies.


Depending on the origin of this anomaly, intrauterine growth retardation can be classified into two types:

1. Intrinsic intrauterine growth retardation . When the causes are specific to the fetus.

2. Extrinsic intrauterine growth retardation . The causes are independent of the fetus. This, in turn, is divided into two groups:

  • Symmetric CIR. When the cause is an inadequate diet on the part of the mother, the fetus is small overall.
  • asymmetric IRC. If the reason is an alteration of the placenta or a disease of the mother, it may happen that the body is smaller, while the head acquires a normal size.

There can also be talk of low-level intrauterine growth (growth is low throughout pregnancy) or late flattening (when the problem arises from the third trimester).


When doctors detect that they may be facing a CIR, they must make certain decisions. Sometimes, the solution is to cause labor to avoid sequelae. Other times, it is enough to monitor the baby until he reaches enough lung maturity to breathe on his own outside the womb. The usual thing in these cases is that a caesarean section is performed so that the baby does not have to go through labor.

Once they are born, the feeding of children with RIC must be monitored. During the first two or three years of life, 85% regain size.

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