When babies are born small for their gestational age (SGA)
When a doctor says your baby is born small for gestational age (SGA), it means that your baby is smaller than expected for the number of weeks they have spent (or gestated) in the womb.

The baby’s gestational age is usually measured from the first day of their mother’s last menstrual period.

SGA is often defined as a birth weight that falls below the 10th percentile for a baby’s gestational age and sex.

This means that only 10% of babies of similar gestational age and sex would have a birth weight lower than that of an SGA baby.

For most term babies born after 37 weeks of gestation, this usually equates to a birth weight of less than 2.5 kilogrammes.

Definitions of SGA may vary depending on the population growth charts or standards used by medical professionals.

An alternative medical definition is a birth weight and/or length that is more than two standard deviations below the mean, or below the 2.3rd percentile.

Reasons for SGA

Babies can be born smaller due to various reasons, including genetic factors, short parents, problems with the placenta, infections during pregnancy, multiple gestations (e.g. twins, triplets), or mother’s health issues, such as high blood pressure, medical conditions, or drugs, alcohol or cigarette use.

A related medical condition is intrauterine growth restriction (IUGR).

This refers to an impairment (restriction) of the baby’s growth while in the womb (uterus), as measured by ultrasound during pregnancy.

It is abnormal, has an underlying cause and needs close monitoring in-utero.

Most babies with IUGR will be born SGA, but not all SGA babies will have experienced IUGR.

It is also important to note that some babies born SGA, who did not experience IUGR, are simply “constitutionally small”.

This means that they are of normal health with no known cause for their small size.

Immediate and early care

Babies born SGA need to be monitored for complications such as breathing problems, temperature (as they are more sensitive to external temperature changes), feeding issues, hypoglycaemia (low blood glucose), jaundice and anaemia.

Complications depend on how low the baby’s birth weight and gestational age are.

It is important to note though that many SGA babies are healthy at birth and have no other issues.

A right balance of nutrition is important for SGA babies.

Adequate nutrition and calories are needed for optimal growth, but at the same time, excessive weight gain should be avoided.

Breastfeeding where possible is encouraged.

Mothers should ideally breastfeed for at least the first six months of baby’s life, as breast milk provides essential nutrients and antibodies to support the child’s needs and immunity.

Breastfeeding may also have a protective effect against obesity and metabolic complications later in life.

Additional dietary supplements might be needed for babies with a very low birth weight or who are born premature.

SGA babies should go for regular check-ups with their paediatricians to monitor their developmental milestones.

These include gross and fine motor (both physical), speech, social, and cognitive skills.

Ideally, they should continue these check-ups until they start formal education in primary school, as subtle learning or behavioural issues may not be apparent during the child’s early years.

Growth and potential complications

Most children born SGA will start catching up with their peers in terms of growth by the age of two to four years with proper nutrition and care.

However, in about 10% of cases, complete catch-up growth does not occur, resulting in a short adult height.

The reason why some SGA children do not catch up in growth is not well understood.

Several possible factors include genetics, nutrition, other health issues, hormones, and physical, social and environmental factors.

Growth hormone treatment is typically considered for SGA babies who are unlikely to have catch-up growth.

These are typically children who remain significantly below their expected height percentiles even after four years of age.

Besides height, growth hormone treatment might have additional metabolic benefits in SGA children.

This includes improvement in body composition, such as increased lean body mass and decreased fat mass.

Growth hormone treatment can help SGA children reach a height within a normal range for their genetic height potential.

However, long-term outcomes may vary, with some responding better than others.

The treatment is generally safe, but like any medication, it may have potential side effects that should be discussed with a paediatric endocrinologist.

A thorough assessment should be done before initiating growth hormone treatment.

Puberty is when a child starts to develop body changes to become an adult.

Some SGA children might be more prone to have earlier or faster progression of puberty.

These differences might lead to more rapid bone maturation and fusion of the growth plates, resulting in a shorter pubertal growth spurt.

This will adversely affect their final adult height.

Hence, children with SGA should have their growth and puberty monitored to ensure normal onset and progression of puberty.

SGA babies may also have a higher risk of developing obesity, type 2 diabetes, abnormal cholesterol levels and heart disease in adulthood.

The reason for this is not well understood and is thought to be due to the “metabolic programming” the baby undergoes while in the womb.

Encouraging children to have healthy lifestyle habits like a balanced diet, regular physical activities and sufficient sleep, can help prevent obesity-related complications as they grow older.

In general, SGA babies require long-term monitoring of their health, growth and development with their paediatrician.

While it is important take note of the unique health issues they may have, it is also important for parents to know that many SGA children thrive, grow and develop normally.

Dr Jeanne Wong Sze Lyn is a consultant paediatrician and paediatric endocrinologist. For more information, email starhealth@thestar.com.my. The information provided is for educational purposes only and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
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This could be due to a number of reasons, but also no identifiable reason at all.