Need to talk? Call 1800 882 436.
It's a free call with a maternal child health nurse. *call charges may apply from your mobile

Is it an emergency? Dial 000
If you need urgent medical help, call triple zero immediately.

beginning of content

Having a small baby

4-minute read

It’s normal for parents to worry about the growth and development of their baby in the womb, particularly if the baby has been measured and is estimated to be 'small'. But does size really matter? Here’s what you need to know if you have been told your baby is, or is likely to be, smaller than average (less than 2.5kg at birth).

Why is my baby small?

The most common reason why a baby is smaller than average — weighing less than 2.5kg at birth — is prematurity< (being born before 37 weeks’ gestation). The earlier the baby is born, the smaller they are likely to be.

This is because the baby will have had less time in the womb to grow. A baby gains much of its weight in the last weeks of the pregnancy.

Some babies don’t gain much weight in the womb because of other risk factors. Having one or more of these risk factors does not mean you will have a baby with low birth weight, but may be at higher risk of having a baby with low birth weight. Risk factors include:

Sometimes a baby is born weighing less than 2.5kg simply because the parents are small themselves or have a certain ethnic background. For example, babies born to Indigenous mothers in Australia are twice as likely to have low birth weight than those born to non-Indigenous mothers.

How is a baby's size measured?

During routine antenatal check-ups, your doctor or midwife may estimate the growth and size of your baby by measuring the fundal height. That is the measurement from your pubic bone to the top of your uterus.

An ultrasound can also give health professionals an idea of how big your baby is likely to be — but it's not very accurate.

There's no way of accurately measuring your baby's weight until after they are born.

A baby's weight is always monitored closely after they are born to make sure they are healthy and growing properly. But their weight isn’t the only thing that’s important. How well they are feeding and the number of wet nappies and poos they produce can indicate whether or not your baby is doing well.

Should I be concerned if my baby is low weight?

Small and large babies can both be born via normal, vaginal delivery, but you and the baby will probably need some extra care both during labour and after the birth. So it’s best to give birth where you can access specialist medical services. Talk to your doctor or midwife about the best place for you to give birth.

If your baby weighs less than 2.5kg at birth, their head may appear to be a lot bigger than the rest of their body. They may look thin with little body fat.

Babies of low birth weight may need to be admitted to the neonatal intensive care unit (NICU) or special care nursery (SCN). Some of the challenges sometimes faced by small babies include:

  • breathing or heart problems
  • low oxygen levels at birth
  • an inability to maintain their body temperature
  • difficulty feeding and gaining weight
  • infection
  • bleeding on the brain (called ‘intraventricular haemorrhage’)
  • problems with their eyes and vision
  • problems with their intestines

These are all more likely to occur in premature babies.

If there are no other complications, low birth weight babies usually 'catch up' in their physical growth. In later life, however, people who were born smaller than average are more likely to develop diabetes, obesity, heart problems and high blood pressure.

Can I prevent low birth weight?

Often there’s nothing you can do to prevent a baby being born small — or large. But looking after yourself during pregnancy is important for all women. You should consider:

Where can I find help?

Always talk to your doctor, obstetrician or midwife first if you have any concerns about your pregnancy, your own health, or the health of your baby.

You can also can call Pregnancy, Birth and Baby on 1800 882 436 to speak to a maternal child health nurse.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: December 2019


Back To Top

Need more information?

Having a small baby

It's normal for parents to worry about their baby's birth weight and growth. Here’s what you need to know if you have been told your baby is likely to be small (less than 2.5kg at birth).

Read more on Pregnancy, Birth & Baby website

Trichomoniasis - Better Health Channel

Trichomoniasis during pregnancy may lead to low birth weight babies and prematurity.

Read more on Better Health Channel website

Pregnancy diet: Foods to avoid

Everyone knows that when you're pregnant, you're eating for two. Less obvious, however, is knowing the particular foods pregnant women shouldn't eat in order to avoid infectious, food-borne diseases, as these can cause miscarriage, low birth weight or a higher risk of Mum getting sick.

Read more on Parenthub website

Milk Bank - Maternal and newborn

The NSW Milk Bank provide pasteurised donor human milk to infants at high risk of Necrotising Enterocolitis when maternal supply is not sufficient to meet the nutritional needs of the infant.

Read more on NSW Health website

Pregnancy - medication, drugs and alcohol - Better Health Channel

Most women take a drug of some kind during pregnancy, sometimes without realising the potential for harm.

Read more on Better Health Channel website

Trichomoniasis - NT.GOV.AU

Symptoms, problems it can cause, tests and treatment for trichomoniasis.

Read more on NT Health website

Premature birth & premature babies | Raising Children Network

This essential guide for parents of premature babies covers gestational age, premature birth risk factors, premature labour and premature development.

Read more on raisingchildren.net.au website

Low-birthweight babies - myDr.com.au

Babies are considered of low birthweight if they weigh less than 2500 g at birth. Low birthweight is associated with a risk of illness in infancy and a long term risk of some chronic diseases.

Read more on myDr website

ACD A-Z of Skin - Pemphigoid gestationis (PG)

Pemphigoid gestationis (PG) is a relatively rare pregnancy dermatosis characterised by blisters

Read more on Australasian College of Dermatologists website

Hernia - Umbilical | Sydney Children's Hospitals Network

What is an umbilical hernia? An Umbilical hernia is an abnormal bulge that can be seen or felt at the umbilicus (belly button)

Read more on Sydney Children's Hospitals Network website

Call us and speak to a Maternal Child Health Nurse for personal advice and guidance.

Need further advice or guidance from our maternal child health nurses?

This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.

The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

Except as permitted under the Copyright Act 1968, this publication or any part of it may not be reproduced, altered, adapted, stored and/or distributed in any form or by any means without the prior written permission of Healthdirect Australia.