Small for gestational age (SGA)

What is Small for Gestational Age?

If a baby is born Small for Gestational Age (SGA), it means they are smaller than they should be in length, weight or head circumference. Approximately 8.6–9.6% of all new-borns are born SGA.

SGA can be caused by several different factors ranging from environmental to genetic.

Most babies with the condition will catch up to a normal length and/or weight by 2 years of age. People born SGA may be at increased risk of developing certain conditions, such as heart disease and type 2 diabetes, which can be prevented through increased awareness and monitoring. Many children born SGA grow up to be adults with normal overall life satisfaction.

Hear advice and tips from other parents whose children are short in stature compared with others their age.

What causes Small for Gestational Age?

Being Small for Gestational Age (SGA) is caused by a variety of factors, with around one third having a genetic cause and the remaining two thirds in response to environmental factors.

Environmental factors that can cause SGA include:

  • Maternal malnutrition
  • Smoking during pregnancy
  • Alcohol consumption by mother during pregnancy
  • Use of recreational drugs such as cannabis or cocaine during pregnancy
  • Maternal inflammatory bowel disease
  • Maternal coeliac disease (a condition where your immune system attacks your own gut tissue when you eat gluten, a protein found in wheat)
  • Maternal epilepsy
  • Placental abruption (a rare condition in which the placenta prematurely separates from the uterus)

If the cause of SGA is genetic, it can be because of a mutation in a number of genes involved in growth plate development. A mutation is a change to a gene that occurs randomly. It is possible the mutation happened entirely by chance in your child for the first time, or it may have been passed down by either parent, who may have been diagnosed as a baby with SGA themselves.

What are the symptoms of Small for Gestational Age?

Characteristics of SGA include:

  • Low birth weight, and/or length
  • Fat accumulation around the stomach
  • In males, small testicles
  • Short stature

Babies born Small for Gestational Age (SGA) are smaller than average in birth weight and/or length. Once born, babies with SGA will often grow at a faster rate than others without the condition. Most catch up in growth by the age of 2, those that don’t will remain short in stature, with average adult height lower than normal.

If your child is short in stature, keeping track of their growth can help identify if there is a problem early on. Compare your child’s measurements to the national average to see if they are within a healthy range.

Calculate your child’s growth

It is important to keep track of your child’s growth in order to identify if there is a problem early on. We recommend measuring your child every 6 months, which is now easier, with our simple to use growth calculator.

Are there any complications associated with Small for Gestational Age?

If your child was born Small for Gestational Age they may be at an increased risk of developing certain conditions, including:

  • Heart disease
  • High blood pressure (hypertension)
  • Type 2 diabetes
  • Issues with temperature regulation
  • Obesity
  • Reduced bone mineral density
  • Kidney abnormalities

How is Small for Gestational Age diagnosed?

Small for Gestational Age is diagnosed at birth based on a series of measurements regarding a baby’s length and/or weight. Birth weight and/or length must be more than 2 standard deviations (SDs) below the mean of other babies their gestational age.

Gestational age is the number of weeks since the first day of the mother’s last period.

Standard deviation is a term used in statistics to describe how much a value differs from the mean, or average, value for the group.

Following a diagnosis of SGA, your doctor will likely closely monitor your child’s growth using a growth chart.

It is important you speak to your doctor if you have any concerns about your child’s height. Use this helpful guide on what questions to ask, and what to expect from your visit.


What’s the difference between Intrauterine Growth Restriction and Small for Gestational Age?

There is a subtle difference between Intrauterine Growth Restriction (IUGR) and Small for Gestational Age (SGA). IUGR specifically refers to reduced rate of growth whilst in the womb prior to birth, it can often be detected through ultrasound measurements.

Some babies may have both conditions, but it is also possible for a baby to be born SGA without experiencing IUGR. Contrarily, babies who have experienced IUGR may not be born SGA.

Do Small for Gestational Age babies catch up?

85–90% of Small for Gestational Age (SGA) babies completely catch up in growth by age 4. Around 10% of children with SGA do not undergo catch-up growth and as adults are short of stature.

Does Small for Gestational Age run in families?

The risk of Small for Gestational Age (SGA) increases if a mother has previously given birth to a baby with SGA. Also, people born with SGA are more likely to have children with SGA also.