Excessive Weight Loss

Almost all infants lose weight in the first few days of life as they lose excess extracellular fluid through diuresis. This can be elevated if the birth parent had intravenous fluids in labour. However excessive weight loss can be a marker of breastfeeding difficulties and dehydration. The average breastfed baby will lose 6-8% of their birth weight, with a maximal loss on day 2 - 3 of life. According to NICE, weight loss above 10% should cause health professionals to pay further attention to how breastfeeding is going, with a detailed feeding history, feed observation and assessment of the baby. Unicef Baby Friendly Initiative-accredited units titrate more intensive breastfeeding support according to the level of weight loss - with routine assessment by a doctor generally recommended at 12.5% weight loss (the 97.5th centile for weight loss in a breastfed baby), unless there is a specific concern about dehydration or underlying illness causing poor feeding. It is notable that some units that devote significant breastfeeding expertise to the management of excessive weight loss use 15% as the medical assessment threshold, unless there is a specific concern.

Good breastfeeding support is associated with less severe weight loss. Early identification of weight loss and good breastfeeding support is associated with less severe maximal weight loss and higher ongoing breastfeeding rates.


The ladder of intervention that should be offered before, or alongside, medical assessment would likely be:

  • Skilled support with positioning and attachment (consider tongue tie assessment)

  • Frequent skin to skin contact

  • Education on feeding cues. At least 8 feeds/24 hours

  • Breast switching - when baby stops swallowing and sucking strongly then switch breasts to stimulate further sucking

  • Breast compression – sustained compression of the breast once the baby has stopped swallowing, in order to increase milk ejection and stimulate further sucking

  • Express milk regularly and give resulting expressed breast milk to baby

  • Express 8-10 times a day and recommend a specific volume of supplement (for example 150ml/kg/day after day 5 of life). When feeding plans are used there should be flexibility around how much supplement to offer based on markers of how effective the breastfeed is

To maximise expressed milk yield, parents can use a hospital grade double electric breast pump, express during or after skin to skin contact, massage the breast before expressing and listen to relaxation tracks or relaxing music (evidence links as for preterm babies).


Babies on this pathway will be weighed frequently to assess their response to breastfeeding support, with paediatric referral if the response is poor. There should also be assessment of potential maternal reasons for low milk supply - for example severe anaemia, retained placenta and thyroid disorder.

As the concern over feeding lessens, it is important for breastfeeding support staff to help the families transition back to responsive feeding with full confidence.

Medical Assessment

The medical concern is that excessive weight loss is associated with hypernatraemic dehydration, which in its most severe form could cause seizures, thrombosis and renal failure. Excessive weight loss is often also associated with more significant jaundice. With very low intake of breastmilk, babies may become hypoglycaemic. Therefore after history and examination, the doctor will consider checking electrolytes, glucose and bilirubin.

Mild hypernatraemia (145-150mmol/l) is present in nearly a third of breastfed infants with all degrees of weight loss and is probably normal in the first week of life.

Severe hypernatraemia (>160mmol/l) is very rare in the UK (<0.001% of births). In a study of all UK cases 2009-2010, no cases of severe hypernatraemia were associated with seizures or death. 94% of these babies had weight loss >15% and average weight loss was 19.5%

The voice of the breastfeeding family

Have a look at Jenny and Michelle's stories of difficulties with weight gain


Thank you for visiting the Hospital Infant Feeding Network. This website is a repository of relevant knowledge and best practice resources for health professionals. To join the conversation, ask questions and share your experiences please join us on Facebook or Twitter.


We will be running Q&A sessions on various topics, which will be advertised on our social media sites. Please email if you have ideas or want to get more involved. We welcome health professionals passionate about supporting breastfeeding and lactation in the hospital setting to join our steering group, please get in contact if this is you!

You may have noticed that we use 'additive' language on our website to refer to lactation and human milk feeding. This means that we might refer to 'breastfeeding/chestfeeding'. Chestfeeding is a term that some non-binary people use to refer to feeding their child at the chest if the word breast is not congruent with their gender identity. Using additive language helps reduce a feeling of exclusion for non-binary and transgender people, without taking away from the importance of words like breastfeeding and mother. There is a much more detailed description of the additive approach here.

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