Author: Katie Knight / Reviewer: Dyanne Imo-Ivoke / Codes: NeoC5, SLO5Published: 12/06/2016 / Reviewed: 27/02/2024

Weight loss and feeding

One of the most common reasons for newborns to be brought into the ED for assessment is weight loss (usually picked up by the midwife on a home visit). It is NORMAL for babies to lose UP TO 10% of their birth weight, but this should be regained by around day 10-14 of life.

How do we work out percentage weight loss?

So, for a baby that weighed 3650g at birth and now weighs 3350g:

(3350 – 3650) ÷ 3650 x 100 = -8.2%. This indicates a weight loss of 8.2%

On arrival at the ED, recheck weight and percentage weight loss as mistakes are common.

Lost more than 10% of birth weight? These babies usually need admission, so get them reviewed by paediatrics.

You will remember Ed Selson’s  tip in his metabolic blog that babies are non-specifically unwell (let’s face it, babies are hardly likely to be specific about anything anyway), for 5 big reasons:

So, with that in mind, it is our job to start thinking of the differentials.

A capillary blood gas is helpful (can be done from a heel prick sample), as this is a quick way to measure electrolytes, lactate and glucose. Babies who have lost weight and have a high sodium need careful rehydration in hospital.

However – any baby referred in, even if weight loss is less than 10%, needs a careful feeding assessment. Review the previous weights recorded in their red book if available.

First things first – the feeding history.

I hope that this is obvious: now is NOT the time to make any comments or judgements on how the parents have chosen to feed their baby, whatever your personal feelings about breast versus bottle. There is no place for unhelpful, upsetting terminology like ‘failure to breastfeed’.

Mums often come under a huge amount of pressure from society/midwives/friends/doctors/families/nosy strangers (delete as appropriate) to breastfeed. If this is something they are struggling to do (or don’t even want to) – it is not your place to push it.

As a paediatrician friend of mine likes to say:

So, is baby being bottle or breast fed? Or mixed feeding? (what proportion of bottle vs breast)? Has this changed since birth?

General questions include:

  • Does baby wake spontaneously for feeds (or cry for feeds) or do parents have to wake baby up?
  • How often is the baby fed? We do not encourage babies to go longer than 4 hours without a feed in the early weeks.
  • Is the baby vomiting (large amounts) after feeds, or just small spit-ups? What colour is the vomit? Is it forceful? (Green or forceful vomit is a surgical emergency, so do ask this specifically, and if it really is green or forceful (projectile) get a surgical review ASAP)
  • Are they burping/winding the baby after feeding? How long does this take?
  • How many wet nappies, and how many dirty nappies per day?
  • What colour is the urine? (red/orange ‘brick dust’ coloured staining in the nappy can be due to urate crystals, a sign that the baby is dehydrated).
  • Has the patient passed any stool since birth? What colour are the stools? (Thick sticky black stools – meconium – are normal to begin with, then they will become lighter, greenish-yellow to bright yellow, and looser (‘seedy’) in texture. (I was going to add a series of links to all these different poo types, but good taste got the better of me. I figure you all know how Google works, right?)

If bottle feeding:

  • How much is the baby taking per feed? (in millilitres, or many parents will still talk about ounces, as this is commonly what’s printed on the side of baby bottles – 1 oz = 30ml)
  • How many hours between each feed?
  • How long does it take baby to finish a feed?
  • How is the milk prepared? Too little or too much water to milk ratio can harm the baby.

If breastfeeding:

  • Has your milk ‘come in’ yet? (if it has, mums will notice nipples leaking, or they may be able to hand express some milk from the nipple – is it colostrum (thin clear yellow liquid) or milk?). Rhythmic sucking and audible swallowing are other signs to show baby is getting a feed from the breast.
  • Is this your first baby? (milk can take up to 3 days to come in, usually quicker if not the first baby)
  • How many hours between each feed?
  • How long does baby stay on the breast for?
  • Is baby alternating between breasts?
  • Is it painful when baby latches on, and if so, has the midwife given you any help with this yet?
  • Does baby seem satisfied after feeding? (If well fed, will usually sleep for several hours after a feed)
  • Do your breasts feel different/less full after a feed?


Aside from the general physical examination, here are a few specific things to look for in a weight loss/poor feeding presentation.

  • Check – with your finger and also look with a pen torch and tongue depressor – for a cleft palate. Wouldn’t want to miss this, and they can’t always be easily spotted like in the picture below.

  • Does the anterior fontanelle appear sunken? This can be due to dehydration. It is good practice to check the anterior fontanelle in any baby presenting to the hospital.
  • Look in the nappy. Is it wet? We expect this to be heavy and clear. Nappies with indicators can detect urine. Is there ‘brick dust’ – urate crystals? This is usually a sign that baby is slightly under-fed. Sometimes parents worry that it is blood – it’s not.

  • Check blood glucose (heel prick BM).
  • Look for jaundice (sclerae/palate) – dehydrated babies are often jaundiced (and vice versa!) If you’re lucky your department might have a gas machine that can measure bilirubin or you may have access to a bilirubin flash machine (bilirubinometer)
  • Put a glove on and check the suck reflex – will the baby suck your little finger?
  • Observe the tongue for a tongue tie. This is particularly important in breastfeeding babies.
  • Is there a patent anus?
Wet Nappies Stools and dirty nappies
Day 1-2: 1-2 or more in 24hrs Day 1-2: 1 or more in 24hrs with meconium
Day 3-5: Should increase by 1 daily, beginning with 3 on the third day and 5 on the fifth day (should also be heavier) Day 3-4: At least 2 (preferably more) in 24hrs with changing stool
Day 6+: 6 or more heavy, wet nappies in 24hrs. Day 5+: At least 2 (preferably more) soft, runny, yellow stools each day

When breastfeeding is more established, some babies may go a few days without passing stool.

‘How much milk should my baby take?’

Every baby is different and some are ‘hungrier’ than others. However – amid acute sleep deprivation and with the overwhelming demands of a newborn, parents often like to be given an ‘exact’ answer. Here’s a way to calculate roughly what baby needs.

Babies need gradually increasing amounts over their first few days of life, and this is calculated as ml per kg per day (always use BIRTH WEIGHT to calculate this number)

As a rough guide:

  • On the first day of life 60ml/kg/d
  • On the second day of life 75ml/kg/d
  • On the third day of life 90mls/kg/d
  • On the fourth day of life 120ml/kg/d
  • On the fifth day of life onwards 150ml/kg/d

So, to calculate what a newborn baby, weghing 3.650kg needs IN TOTAL on day 1

60 x 3.650 = 219ml (round up to 220ml)

Divide this into amount per feed (and round the numbers to make it easier for sleep-deprived parents to understand).

If this baby is feeding every 3 hours, (220 / 24) x 3 = 27.5ml per 3-hourly feed (call it 30ml)

If this baby is feeding every 4 hours, (220 / 24) x 4 = 36ml per 4-hourly feed (call it 35ml)

These calculations are a GUIDE, and what a healthy baby takes can vary from baby to baby, and from feed to feed.

Clearly it’s much easier to work out what a bottle-fed baby is taking. If a mum is breastfeeding and is concerned about baby’s intake, it can be helpful to suggest hand expressing milk (or using a breast pump) so that she has an idea of how much milk she is producing.

Going home?

Less than 10% weight loss, with a normal physical examination and nothing else concerning in the history – these babies are usually just taking time to establish their normal feeding pattern. It is usually appropriate to send these babies home with careful safety netting if a feeding plan is in place. A feeding plan usually covers the amount of milk baby is expected to take per feed or per day, and sometimes a plan for supplementing (‘topping up’) breastfeeds with formula milk if there may be a lack of breast milk supply.

Always run things by the paediatric team if you’re unsure.

Give the parents a written feeding plan.

Encourage them to keep a feeding diary for a few days, as this will be a good way for them to start to see patterns in how their baby likes to feed. Record feed time, amount, vomit, wet nappies, and dirty nappies.

The midwife should be visiting again within the next few days to check baby’s weight (ideally within 48 hours)– call them and confirm when this is going to be. The midwife is also the best person to help with breastfeeding techniques.

Safety netting – ask parents to come back if baby:

  • Is going longer than 4 hours without a feed
  • Not passing urine at all (at least 1 in a 24-hour period)
  • Is vomiting large amounts or vomit is green or forceful
  • Is lethargic, floppy, or difficult to rouse.
  • Has a fever
  • Appears more yellow
  • Has a rash

This may be obvious to you, but it isn’t always to them, so be helpful and point it out anyway: they are probably deprived of sleep (like you).

References/Further reading

  1. Denne SC. Neonatal nutrition. Pediatr Clin North Am. 2015 Apr;62(2):427-38.
  2. Tawia S, McGuire L. Early weight loss and weight gain in healthy, full-term, exclusively-breastfed infants. Breastfeed Rev. 2014 Mar;22(1):31-42.
  3. Team DFTB. Neonatal checks demystified: how I do a baby check, Don’t Forget the Bubbles, 2021.