Newborn Weight Loss – 6 Things You Need To Know

Newborn Weight Loss - 6 Things You Need To Know

It’s normal for babies to lose weight after birth.

Conflicting opinions exist, however, with regards to up to what percentage of weight loss is normal and about when supplementation may be necessary.

Here are 6 things you need to know about newborn weight loss and what is ‘normal’:

#1: It’s Important Not To Compare Apples With Oranges

When determining what is normal, it’s important to keep in mind that breastfeeding is the biologically normal way to feed babies. Hence, what healthy, full term, exclusively breastfed babies do must be the benchmark we use. Else the control to which babies who are not exclusively breastfed becomes the comparative norm.

Therefore, deciding if a baby is losing too much weight after birth needs to be determined by taking into account what is normal for healthy, full term, exclusively breastfed babies, and not babies who are mixed fed or formula fed.

#2: It Takes Time For Your Milk To Come In

Around day 3 after a mother gives birth, her milk ‘comes in’ and she starts to make increasingly larger volumes of milk. Before this time, a baby drinks small amounts of colostrum frequently. Colostrum is a concentrated source of protein and anti-infective factors. It’s all that is needed for a healthy term baby.

Babies have inbuilt ways to maintain their water, glucose and energy levels until large volumes of milk are available.

There’s generally no need to worry about early weight loss. One your milk has come in and the volume of milk your baby drinks increases, he will keep gaining weight.

#3: Weight Loss Has A Range Of ‘Normal’

According to the Royal Women’s Hospital Clinical Guideline, ‘Breastfeeding the healthy term baby’:

“Loss of 7-10% of birth weight is normal in the first few days of life”.

Some have warned about the use of an absolute percentage that a baby can safely lose after birth. This is because an absolute percentage doesn’t take into account the normal range of percentages.

#4: Regaining Birth Weight

In terms of the time it takes babies to regain birth weight, the Academy of Breastfeeding Medicine clinical protocol #3 says:

“Optimally breastfed infants regain birth weight at an average of 8.3 days (7.7–8.9) with 97.5% having regained their birth weight by 21 days”.

#5: Intravenous Fluids In Labour Transfer To The Baby

Fluids given to a mother during labour cross the placenta to the unborn baby.

Many studies have shown that a baby’s birthweight can be artificially elevated due intravenous (IV) fluids given to the mother during labour.

This could make it seem like a baby is losing more weight than they are supposed to (and perhaps lead to unnecessary supplementation and a dent in the mother’s confidence in breastfeeding). And yet, all they may actually be losing is the excess fluid they have on board due to the IV fluids given to the mother during labour.

For this reason, it has been suggested that it may be better to weigh a baby at 24 hours after birth (when the excess fluid has been passed) rather than at birth.

This is important, since getting IV fluids during birth is very common these days. For example, IV fluids are given for:

  • Epidural
  • Labour induction
  • C-section
  • Group B strep antibiotics

#6: IV Fluids May Cause Breast Swelling And Feeding Issues

In addition, the use of IV fluids during labour may result in generalised swelling, including of the breast. Any swelling of the breast affecting the areola and nipple can make it harder for a baby to attach to feed. Breast swelling may even contribute to a delay in a mother’s milk ‘coming in’.

Important Note

Sometimes, excess newborn weight loss may be a sign of a baby not getting enough milk or an underlying medical condition. However, weight measurements should not be the only tool for assessing and making clinical decisions.

A complete evaluation is required, including assessing the baby’s output (poos and wees), oral anatomy, breastfeeding frequency and effectiveness etc.

It’s advisable that you seek an assessment from a healthcare professional if you have any concerns that your baby’s weight may be related to a health condition.

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Renee Kam is a mother of two daughters, an International Board Certified Lactation Consultant (IBCLC), a physiotherapist, author of 'The Newborn Baby Manual' and an Australian Breastfeeding Association Counsellor. In her spare time, Renee enjoys spending time with family and friends, horse riding, running and reading.


  1. I am a midwife working in a MGP. Found this article very interesting. In particular about weight gain or loss associated with IV fluids in labour. This is something I notice happens from time to time. Would be interested in a follow up article covering what to do when weight loss exceeds the 10%. Also interesting the extended time to regain birth weight.

    1. Hi so my newborn weighed 8lbs 12oz at birth which was september 3rd and i went to the peds yesterday and she is down to 8lbs 4oz what is your opinion i only bottle feed.

    2. I was given over 2 litres of fluids while waiting for my c-section as my BGL had dropped to 2.9
      My baby was born weighing 9pd 2 oz. When he was weighed 5 days later he was down to 8pd 1 oz. Even though i had been demand feeding him from birth, which pretty well felt like he was on.the breast constantly. I had great supply and he was a hungry baby. It put that much of a dint in my confidence in myself, my milk and breastfeeding in general that i dried my milk up and formula fed him. Reading this has just devastated me. One midwife suggested that thos may be the case but it was dismissed by pretty much everyone else.

  2. Hi. I am an IBCLC working in hospital. And i noticed many cases referred to us by the baby peads doctor with concern on slow weight gain, do take 21 days to regain thier birth weight. It is good to know reasons behind that lose and slow gaining from different perspectives…thank you for sharing such knowledge

  3. Thank you for this article as I have been so worried there is something wrong with my little one! He was born 9lb 3oz (c section) and 3 days later he was 8lb 5oz. He is now 14 days old and still miles away from his birth weight. The midwife and health visitor have both seen me feed him and say that he is well latched on and feeding well (30 mins every 3 hours) and he is pooing about 8-10 times a day. They have however told me that he should have regained his birth weight by 2 weeks, which clearly hasn’t happened. My husband and I both feel his birthweight was inflated (he was very very swollen and puffy) and are now more comfortable waiting another week to see how he goes.

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