Did you know that newborn babies lose weight after birth?


A baby’s weight is one of the first things people ask about your newborn (after you’ve told them whether you had a boy or a girl, of course!) Weight tends to be an indication of how ‘healthy’ a baby is, when in reality the weight of a baby at birth depends on many factors, including mum’s own weight and diet, mum’s ethnicity and whether the baby is her first or a subsequent baby (first babies tend to be smaller than their siblings).

Knowing and recording the baby’s weight at birth is important, and how much they weighed at birth is something we tell our children throughout their lives, but what we don’t all realise as new parents (and we’ve all been there!) is that babies do lose some of that weight in the first few days after birth.

Of course they do gain it back, and how much they lose and how long they take to gain it all back are important indicators of how well a baby is feeding in the first few weeks after their birth.

Read on to find out why…

Why do babies lose weight after birth?

The initial weight loss in babies is caused by fluid loss. We need to remember that because babies’ stomachs are so tiny at first, and they can only have a small amount of milk or colostrum, the amount they drink is not enough, at first, to make up for that initial loss of fluids. This is why it takes them a few days to regain their birth weight.

How long does it take for a baby to regain their birth weight?

This depends on the baby, of course, and on how much weight they lost in the first place, but on average babies should take 10-14 days to regain their original birth weight. If they lost more than what is considered the ‘average amount’ or if they are sick or premature, it might take them longer to regain it.

How much weight do they lose?

The initial amount of weight a newborn can lose ranges from about 5% to approximately 10% of their original birth weight. So if a baby weighs 3.35kg at birth, for example, it would be considered ‘normal’ for them to lose up to 335gr. Their weight in the first week or so after the birth could drop to approximately 3.015kg, and this would be considered completely ‘normal’.

What happens if they lose more than 10% of their original birth weight?

It depends on how much more they lose, of course, but because the time taken for a baby to regain their birth weight, and the time taken to establish a pattern of weight gain are considered important by health professionals in the UK, a loss that is greater than 10% of the original birth weight (or the fact that a baby might take longer to regain that weight) would be monitored.

Is it dangerous for a baby to lose more than 12% of their birth weight?

A weight loss of more than 12% of the original weight would be considered ‘excessive’ and potentially dangerous. This is because excessive loss of fluids that are not equally replenished could cause dehydration – this causes the blood to thicken, and the baby’s heart has to work harder. Plus, in extreme situations, vessels that are leading to vital organs can clog up and create a real danger to the baby.

The excessive fluid loss may also cause sodium levels to increase, and when sodium levels are too high, they can poison the cells. The combination of dehydration and increased sodium levels is actually quite dangerous, as it can affect brain cells and cause the baby to have fits and behave abnormally.

But that is what an ‘extreme’ situation looks like, and in order to prevent that from ever happening, your midwife and health visitors will make sure that your baby’s weight is monitored in the initial days and weeks after birth.

Why would a baby lose excessive weight or not regain their birth weight within the first 14 days?

There are few reasons that could cause a baby to lose more than the ‘tolerated’ percentage of up to 10%. For example:

  • Insufficient feeding – for the breastfed baby, this could be the result of undetected poor positioning or poor latch at the breast.
  • Infrequent feeding – it is very important that babies are ‘fed on demand’, which means feeding your baby when they appear hungry, as advised by health professionals. Imposing set times for feeding or missing feeding cues could reduce the baby’s milk intake excessively.
  • An underlying illness (symptoms of which could be irritability and fever).

What can health professionals do if a baby is losing too much of their birth weight or not regaining it by 2 weeks after birth?

Midwives and health visitors are trained to keep an eye out for any issues that might contribute to creating a situation of excessive weight loss.

Amongst others, things that they look out for are:

  • How the baby latches onto the breast (positioning and latch) and how the baby feeds while at the breast – do they stay attached to the breast or slip off it? Are they swallowing milk rhythmically? Are they calm while feeding?
  • How the baby looks and behaves otherwise – are they alert, responsive and content, rather than ‘floppy’ or restless or fussy?
  • How mum looks and behaves when feeding – does she look relaxed and comfortable or tense and uncomfortable? Do her breasts look soft or hard and inflamed? Do her nipples look healthy or sore and cracked? Can she see the baby feeding on the breast? Can she recognise what a ‘good’ latch looks like?
  • Is the baby producing enough wet and dirty nappies – the ‘output’ is a clear indication of the ‘input’, or in other words, how well the baby drinks. This is why new parents will always be asked by midwives how many wet and dirty nappies per day the baby has. This doesn’t mean that parents should obsess about recording an exact number every single day, but broadly keep tabs on the baby’s nappy content is important. Every baby is different, but on average a new baby may have anything between 5-10 wet nappies over a 24 hour period and 3-5 dirty ones, with formula-fed babies perhaps having a little less dirty nappies than the exclusively breastfed ones.

What happens when any areas of concern are detected from the mum and baby observations?

If any of the above points create any concerns, a midwife, lactation consultant or peer supporter should be able to help by advising the parents on how to improve the situation. The right information, help and support, tailored to each individual family should be offered, and often it can be a matter of spending more time with the family to help mum with latch and positioning.

However, it’s important for new parents to know that even in the absence of any concerns, their baby will be weighed often in the first 10-14 days after birth. Weighing too often and without a particular reason can create anxiety in the parents, but we hope that this article explains the reasons why this is done.

What can parents do to prevent an excessive weight loss in their babies?

  • Be informed and proactive – have the right expectations around how newborn babies feed and, if they are breastfeeding, on how breastfeeding works, including understanding the supply and demand mechanism, milk composition and learning to recognise the signs of a good latch (curled out lips, round cheeks, chin indenting, regular swallowing etc.).
  • Have confidence in mum’s ability to breastfeed – this is very important for both mum AND dad and for whoever is around to help and support mum after the birth of the baby.
  • Have plenty of skin-to-skin contact with their baby – it’s great for bonding and for baby’s metabolism, and it will help the parents recognise (and act on) their baby’s feeding cues as well.
  • When breastfeeding, in the first few days and weeks in particular, parents can try and ensure that their baby feeds often from both breasts and has a good number of feeds over the 24-period (8-12 feeds are considered ideal for this period).
  • Know when and where to ask for help – cracked and bleeding nipples and a distressed baby are signs of poor latch and positioning. If there’s anything that parents can do to get support before their next scheduled midwife appointment, if they feel this is what is required, they should try and do so.
  • And last but not least, they should try and relax and enjoy their baby – babies pick up on our emotions, and if we are stressed and tense, they pick up on this!

This is it from us – we hope you found this article useful, and next time we will talk about weight gain and weight monitoring in the first months after birth and what this means for parents.

In the meantime, please share your experiences with us. Do you know how much weight your baby lost? How long did it take them to regain their original birth weight?

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