Regular monitoring of your baby’s growth can be a great way to make sure your baby is on track and healthy through gestation, when they’re born and during their first few years of life. This is where baby weight percentiles come in.
A healthy birth weight is one indicator that medical staff use to make sure your baby’s growth and development are on track. This is just one of several different measurements that are used to assess the health of newborns, along with their length and head circumference. Want to learn more? Read on to discover why baby birth weight is important and how these standards are used.
Why is baby birth weight important?
Birth weight is used by medical professionals to measure a newborn's nutrition, health and development1. Birth weight provides insight into your baby’s overall wellbeing at birth. This tracking begins during gestation, with regular measurements used to monitor their development and growth. Once they’re born, their weight will continue to be measured at regular intervals up until their first birthday. Some babies may require more frequent checks depending on their health. Ultimately, you want your baby to be delivered at a ‘normal birth weight.’ If their birth weight is too low or too high, they could be at higher risk of potential health issues or complications.
How much should my baby weigh at birth?
In Australia, healthy birth weight ranges from 2,500 and 4,499 grams1 or 2.5kg and 4.49kg. However, just because your baby’s weight is lower or higher than the average baby weight range doesn’t necessarily indicate that there’s an issue. You should always take the advice of your healthcare professional when it comes to your baby’s weight.
The average baby weight at birth typically depends on several factors, including2:
- How close they were born to their due date
- Their gender - male babies can be larger
- Birth order - the first born baby can be smaller
- Your general health and whether you experienced pregnancy complications
- If your baby is a multiple - e.g twins or triplets
- You and your partner’s height and weight2
What’s considered a big baby at birth?
A big baby is a baby that typically sits outside of the normal baby weight range. With this in mind, a big baby size in Australia is typically considered to weigh more than 4,000-4,500 grams at birth1.
While most large babies don’t have a difficult birth, there are potential implications for both mum and bub. You may find it takes longer to deliver a big baby and there can be an increased risk of birth injury, like perineal tears and shoulder dystocia3. Large babies are also at higher risk of breathing issues, low blood sugar and birth injuries, like broken collar bones or damaged shoulder nerves due to shoulder dystocia4.
Why do babies lose weight after birth?
It’s completely normal for newborns to experience weight loss of around 10% in the days following birth, which is usually due to fluid loss or feeding adjustments5. From about three to four days, newborn weight loss should stop and most infants will have returned to their birth weight by three weeks of age6.
However, keep in mind that all babies are different, which is why they’re weighed frequently during the first few months of life to make sure their growth is on track. However, some babies like those with low birth weight, may be weighed more often. As a parent, it’s important to make sure you take your newborn for their scheduled check-ups to make sure they’re growing as expected.
Baby weight percentiles in Australia
In Australia, it’s common practice for baby percentiles to be used when tracking the growth of newborns. Percentiles are used to compare a baby’s weight with that of other babies of the same age and gender, helping healthcare providers track how the baby is growing over time.
The World Health Organisation (WHO) has developed a range of growth charts that are often used by healthcare providers around Australia. The charts include a range of percentiles, like the 3rd, 50th and 97th, to indicate a healthy trajectory of growth. For example, a baby that falls in the 90th percentile weighs more than 90% of babies. A baby in the 10th percentile, on the other hand, weighs more than just 10% of other babies the same age and gender.
If in doubt, you should always speak to your doctor for advice and guidance that’s relevant to you and your baby.
What is a good percentile for baby weight?
Even though growth charts and baby percentiles are used to track baby weight, there’s no ‘ideal’ baby weight. Healthy babies come in all shapes and sizes, so long as they follow a consistent growth trajectory on their percentile curve, that’s all that matters.
How is the baby weight percentile measured?
Your baby’s weight percentile is calculated using special baby scales, which is then compared against the relevant percentile chart. In addition to their weight, your doctor will usually check their head circumference and length/height too.
These measurements are typically taken at routine checkups, which usually happen in the days following birth, at one to two weeks old, and every month until they’re six months old. After this point, they’ll be measured every two months until they’re 12 months old, and then every three months until their second birthday2.
Regular measurements allow your doctor to plot your baby’s weight against the growth chart, providing a visual representation of their growth relative to other babies of the same age and gender.
It’s important not to get too caught up with the specific percentile. Instead, healthy babies should follow their own specific growth trajectory. However, if you have any concerns about your baby’s weight or development, be sure to seek medical advice and guidance.
To learn more about pregnancy, birth and raising a newborn, head to our Parent’s Lounge.
References:
- Australian Institute of Health and Welfare. Australia’s mothers and babies, Birthweight. Australian Institute of Health and Welfare. 2023. Available from: https://www.aihw.gov.au/reports/mothers-babies/australias-mothers-babies/contents/baby-outcomes/birthweight
- How your baby gains weight. Healthdirect.gov.au. Healthdirect Australia; 2024. Available from: https://www.healthdirect.gov.au/how-your-baby-gains-weight#typical
- Australia H. Having a large baby. www.pregnancybirthbaby.org.au. 2021. Available from: https://www.pregnancybirthbaby.org.au/having-a-large-baby
- Large for Gestational Age - Health Encyclopedia - University of Rochester Medical Center. Rochester.edu. 2019. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02383
- Guidelines for weight gain in babies. Nourish Baby Online. 2022. Available from: https://nourishbaby.com.au/blogs/blog/guidelines-for-weight-gain-in-babies
- Alliance (UK) NG. Weight loss in the early days of life. www.ncbi.nlm.nih.gov. National Institute for Health and Care Excellence (UK); 2017. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536449/