top of page


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/chestfeeding 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/chestfeeding is going, with a detailed feeding history, feed observation and assessment of the baby. Unicef Baby Friendly Initiative-accredited units titrate more intensive feeding support according to the level of weight loss - with routine assessment by a doctor/ANNP 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 lactation 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/chest switching - when baby stops swallowing and sucking strongly then switch to the other side to stimulate further sucking

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

  • Express milk regularly and give resulting expressed 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 feed is

To maximise expressed milk yield, mothers/parents can use a hospital grade double electric pump, express during or after skin to skin contact, massage the breast/chest 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 feeding support, with paediatric referral if the response is poor. There should also be assessment of potential maternal/parental reasons for low milk supply - for example severe anaemia, retained placenta and thyroid disorder. This article suggests that TSH should be checked in all mothers with unexplained breastfeeding difficulty in the first 12 weeks after birth to look for postpartum thyroiditis.

As the concern over feeding lessens, it is important for 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 may also be associated with more significant jaundice. With very low intake of human milk, babies may become hypoglycaemic - particularly if they have other risk factors for hypoglycaemia such as low birth weight. 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/chestfeeding family

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

bottom of page