by Scholten A


A baby who is small for gestational age (SGA) has a lower weight than normal for the number of weeks of pregnancy. Sometimes this raises the risk of early birth, low birth weight, miscarriage and other problems.

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SGA may be caused by growth problems before birth. This can be due to:

  • Lack of nutrients and oxygen to the baby
  • A small uterus
  • Exposure to certain substances
  • Infections or long term illnesses during pregnancy
  • Birth defects
  • Problems with genes

Sometimes a baby is small because the parents are small. These babies have normal growth. They are just small compared to others their age.

Risk Factors

SGA is more common in mothers who have had a prior SGA baby.

During pregnancy, problems in the mother can raise the risk. They include:

Other things that raise the risk are:

  • Pregnancy with more than one fetus—such as twins or triplets
  • Birth defects or genetic problems in the baby


Symptoms of SGA are a weight that is in the lowest 10% of babies with the same gestational age.


A baby with SGA is often diagnosed before birth. A physical exam will be done on the mother. Measurements will be taken of the mother’s belly, weight, and uterus (womb). They are based on the number of weeks of pregnancy. If the measurements are low, the baby may be smaller than average. SGA may also be diagnosed at birth based on the baby’s weight and height.

Images may be taken during pregnancy with an ultrasound.


The goal is to watch for and treat problems in the mother and baby.

Babies that have SGA from lack of nutrition or oxygen may need treatment. Options are:

Before Delivery

The doctor may:

  • Monitor the baby’s growth
  • Deliver the baby early— if growth problems are severe
  • Treat health problems in the mother

After Delivery

Babies who are born with SGA may be weak. They may not be able to feed enough or stay warm. Treatment may include:

  • Using warming beds or incubators
  • Tube feedings
  • Checking oxygen levels

Monitoring and treatment may also be needed during childhood.


SGA cannot be prevented when due to genes, syndromes, or problems with the uterus.

Otherwise, pregnant women may reduce the baby's risk of SGA by:

  • Taking folic acid
  • Not smoking, drinking alcohol, or using drugs
  • Having early and ongoing prenatal care
  • Getting care for long term health problems


American Pregnancy Association 

Healthy Children—American Academy of Pediatrics 


Canadian Paediatric Society 

Health Canada 


Intrauterine growth restriction. EBSCO DynaMed website. Available at: Accessed February 10, 2021.

Intrauterine growth restriction (IUGR); Small for gestational age (SGA). American Pregnancy Association website. Available at: Accessed February 10, 2021.

Small for gestational age babies. Patient UK website. Available at: Accessed February 10, 2021.

Small for gestational age introduction. The MAGIC Foundation website. Available at: Accessed February 10, 2021.

7/7/2016 DynaMed Plus Systematic Literature Surveillance.  : Pamidi S, Marc I, et al. Maternal sleep-disordered breathing and the risk of delivering small for gestational age infants: a prospective cohort study. Thorax. 2016 Apr 15.

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