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What’s normal with weight gains?

Having your breastfed baby weighed can be a worrying time

baby on scales

Many mums worry about their baby's weight gains. This is made more stressful by the unhelpful focus that we put on weight gains and losses, combined with a lack of understanding about what's normal.

What is normal weight gain for breastfed babies?   

The general guidelines for weight and growth measurements are: 

  • A baby loses up to 10% of their birth weight in the first week and regains this by 2 weeks. 

  • Birth weight is doubled by 4 months and tripled by 13 months in boys and 15 months in girls. 

  • Birth length increases 1.5 times in 12 months. 

  • Birth head circumference increases by about 11 cm in 12 months. 

The World Health Organization growth standards are the best reference for growth in the first 2 years as they reflect the growth of healthy breastfed babies. 

However, all babies grow differently and these are just general guidelines. If you are concerned about your baby's growth, have a check up with your doctor.  

Why has my newborn lost weight?

It’s normal for babies to lose weight after they are born, no matter what or how they are fed. You can expect your breastfed baby to lose weight for the first 3 or so days. It’s normal for a baby to lose up to 10% of their birth weight in the first week.

Babies are made to survive on the small volumes of colostrum they receive in the first few days. Once your milk comes in, you will begin to make a large amount of breastmilk which then provides all the fluids, energy and nutrients that your baby needs to regain their birthweight by about 2 weeks of age. 

If your baby has lost some weight, it’s important for your health care providers to look at the overall picture of you and your baby. For example, a 2-day-old baby who has lost 10% of their birthweight and who is sleepy and not feeding well will need a lot of support. A baby who has lost 10% but is feeding often and well may not.  

If I have IV fluids will it affect my new baby's weight?

Some research suggests that a baby may be born with excess fluids if the mum had intravenous (IV) fluids during labour. These fluids would pass out of the baby's body in their urine after birth, making it look as if they had lost a lot of weight quickly. This may be more likely to happen when larger volumes of fluid are given. 

IV fluids are often given along with other birth interventions. We still need more research to confirm if the typical volumes of IV fluids given to women cause healthy, term, exclusively breastfed babies to show large weight losses. More research is also needed to help us understand if other factors, such as the way a baby is born, make this more likely.

How do breastfed babies grow?

World Health Organization (WHO) growth charts used in Australia are based on the length and weight of normal, healthy, breastfed babies. There are charts for weight, length and head circumference, which are plotted as the baby grows. Older charts were based on a mix of breastfed and formula-fed babies, each with different growth rates. These may still be used in some places, so check that your baby’s growth is being plotted on the WHO charts.  

Some important things to know about how breastfed babies grow:

  • In the first 3 months, breastfed babies usually gain weight slightly faster than formula-fed babies.  

  • From 3 to 4 months onwards, their weight gain slows down compared to babies who are fed formula. So if your 4-month-old baby looks like they are no longer gaining weight at a rapid rate, there may be no need to worry.  

  • Weight gains can vary from week to week. However, your baby should grow steadily over their first year. It may be helpful to look at average weight gain over a month. 

  • At 1 year, breastfed babies are on average lighter. 

  • Not all people are the same size and shape. A baby born to small parents may have slower weight gains. 

  • Growth is not all about weight. Your baby's length and head circumference should also be checked. Sometimes a baby may have a low weight gain but may have grown a lot in length. 

When you’re looking at the growth charts, remember that the 50th percentile on the chart is an average, not a ‘pass’ mark or something to aim for or exceed. It means that 50% of normal babies will be below that line and 50% above. 

Commonly asked questions about weight gains

My baby continues to have low weight gains. Are they getting enough breastmilk?

If you are worried that your baby isn't gaining enough weight, you're probably also worried about your milk supply. These are some reliable signs that your baby is getting enough. 

  • After 5 days of age a minimum of 5 heavily wet disposable, or 6 to 8 very wet cloth nappies in 24 hours. 

  • Pale urine (wee). If your baby's urine is dark and smelly, this is a sign that your baby is not getting enough milk.  

  • Good-sized, soft poos. Under the age of 6 to 8 weeks, your baby should have three or more runny poos a day, about the size of the palm of their hand. After this age, it can be normal for a baby to poo less often, even once every 7 to 10 days. When your baby finally does a poo, it should be soft or runny and there will likely be a large amount!

In addition to the 'what goes in must come out' signs above, other reliable signs that show your baby is getting enough milk are: 

  • Your baby has some weight gain after the initial weight loss soon after birth, and some growth in length and head circumference. (Are your baby's clothes getting more snug?) 

  • Your baby looks like they fit their skin, with good skin colour and muscle tone.   

  • Your baby is meeting developmental milestones. 

If you’re concerned that your baby isn't getting enough milk, there are things you can do to increase your supply.

My baby was gaining weight well and suddenly things have slowed down. What's going on?
  • Is your baby feeding often enough? In the first few months, most babies need at least 8 to 12 feeds (or more) in 24 hours to take in enough milk.

  • Have you only been offering one breast per feed?  Some babies start off just needing one and change as they grow older. You could try offering your baby the second breast at each feed. 

  • Has your baby been taking fewer feeds recently, perhaps because they are sleeping longer at night?  

  • Have you been trying to feed at set times instead of when your baby wants to? They may not be taking as much breastmilk as they were.  

  • Is your baby attaching and sucking effectively? Babies who are failing to thrive may have a poor sucking action, so they don't empty and stimulate your breasts enough. 

  • Have you been stressed or unwell? Started a new medication? Hormonal changes? For some mums these can cause a temporary dip in supply. 

  • Has your baby previously gained well and is now slowing down normally? It is very normal for an exclusively breastfed baby's weight gain to slow down at 3 to 4 months. The World Health Organization child growth standards show this. 

If your baby has a sudden weight change, but they seem happy and all other signs of growth and health are fine, you may like to just 'wait-and-see'. You could offer a couple of extra breastfeeds a day to help avoid a more serious situation.   

My baby is getting enough breastmilk. What's causing the low weight gains? 

If your baby appears to be underweight, with wrinkly, loose skin but they have a good nappy count, there may be an underlying medical condition which is causing a slow weight gain. Some common conditions which can affect weight gain include:   

  • infection (anything from a cold to a urinary infection) 

  • vomiting or frequent posseting can mean a baby does not keep down enough milk to grow

  • a severe allergy to foods in the mother's diet could be a cause of low weight gain.

Your doctor can help you check out these and other possible causes.  

What about test weighing?

Test weighing involves weighing the baby before and after a feed, to give an idea of how much milk they are getting and therefore what your milk supply is like. For test weighing to be useful in judging milk supply, it must be done at every feed for 24 hours. Weighing after just one feed won’t tell you anything about your supply or how much milk your baby needs. Counting wet and dirty nappies will tell you if your milk supply is enough for your baby.  


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Noel-Weiss, J., Courant, G., Woodend, A.K. (2008). Physiological weight loss in the breastfed neonate: A systematic review. Open Medicine, 2(4), e99–e110. 

Bertini, G., Breschi, R., Dani, C. (2015).Physiological weight loss chart helps to identify high-risk infants who need breastfeeding support. Acta Paediatrica, 104(10), 1024-1027 

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Noel-Weiss, J., Woodend, A.K., Peterson, W.E., Gibb, W., & Groll, D.L. (2011). An observational study of associations among maternal fluids during parturition, neonatal output, and breastfed newborn weight loss. International Breastfeeding Journal, 6, 9. 

Margot Giudicelli, Michelle Hassler, Julie Blanc, Carole Zakarian & Barthélémy Tosello (2022) Influence of intrapartum maternal fluids on weight loss in breastfed newborns, The Journal of Maternal-Fetal & Neonatal Medicine, 35(4), 692-698.

Watson, J., Hodnett, E., Armson, B. A., Davies, B., & Watt-Watson, J. (2012). A randomized controlled trial of the effect of intrapartum intravenous fluid management on breastfed newborn weight loss. Journal of Obstetric, Gynecologic, and Neonatal Nursing, 41(1), 24–32.

Eltonsy, S., Blinn, A., Sonier, B., DeRoche, S., Mulaja, A., Hynes, W., Barrieau, A., & Belanger, M. (2017). Intrapartum intravenous fluids for caesarean delivery and newborn weight loss: A retrospective cohort study. BMJ Paediatrics Open, 1(1), e000070.

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© Australian Breastfeeding Association April 2022