Everything you always wanted to know about newborn baby poo: constipation, diarrhoea and colours

Our baby poo bible will help you get to the bottom of what’s happening in your baby’s nappies. Puns intended.

In Newborn

    2-minutes read

    At a glance

    Black poos. Be prepared for some of these in your baby’s first days – it’s called meconium

    Breastfed baby poos are usually runnier than those fed with formula especially before weaning


    A tummy massage can help get things moving down there – useful if baby’s constipated

    Diarrhoea can lead to dehydration so it’s very important to top up baby’s fluids

    Who knew poo would be such a topic of conversation? With all the changes that are going to happen in your baby’s nappies over time you may find yourself Googling the number two, weaving it casually into conversation and perhaps even showing your newborn's baby poo photos to your partner or health visitor. Find out if what you’re wiping up is normal after we take you through all things poo.

    What does normal baby poo look like?

    Newborn baby poo, like wine, will mature with age. The first few nappies may not be what you expected because they are usually black or dark green and a strange, sticky texture. This is called meconium. It’s all the stuff that baby ingested while in the womb: delicious things like bile, mucus, water and lanugo - the name for the soft hair that once covered their body.

    A few days later, once they’re full of milk, the nappies will start to turn yellowish. If you’re breastfeeding it can be watery, mustard-like poo. If you’re formula feeding it will be a bit darker, firmer… and whiffier.

    How many nappies are we talking?


    If you’re breastfeeding you can expect a lot of nappy changes. Up to a dozen a day isn't abnormal. It can seem like it’s literally in one end and out the other for every single feed, especially in the first month. If you’re formula feeding there might only be a poo once a week or so. Formula-fed babies will generally do fewer poos but their nappies may have a stronger scent.

    The dirty nappy rate should slow down a bit for most babies once they’re around a month old.


    Infant constipation must feel really uncomfortable and the poor little things haven’t a clue what’s going on. Here’s a few signs that could show they’re constipated:

    • Dry or hard stools
    • Strong-smelling wind
    • Infrequent dirty nappies
    • Loss of appetite
    • Lethargy and grumpiness

    What causes it?

    • Dehydration – if your baby’s not getting enough fluids this can result in drier stools.
    • Moving on to solid foods – any changes in their diet could change the contents of their nappies. They might have firmer, darker poos but it will vary according to what they are eating.
    • A reaction to a certain formula – formula-fed babies, in general, don’t poo as often, so there’s no need to worry if it’s been a few days. Talk to your GP if you’re concerned and they may recommend trying a different kind. It could even be that baby’s not getting enough milk or their formula may have not been prepared correctly.
    • Some breastfed babies go a few days without a dirty nappy but this doesn’t mean they’re constipated. Every baby is different so this might be their normal.
    • An underlying illness – a change in your baby’s poos could be a sign your baby is unwell but as always it’s best to talk to your GP if you’re in any way concerned.

    In general, breastfed babies are rarely constipated due to the natural laxative effect of breast milk.

    How can I help move things along?

    Hopefully it will pass (literally) with time. If your infant's constipation continues and your baby is in pain then speak to your GP, health visitor or a public health nurse. They will often recommend giving baby some cool boiled water. They may even suggest changing baby’s milk or in extreme circumstances, they may suggest using a laxative suitable for young babies. Tummy massages can help too: clockwise hand movements on their tummy, and slow downward strokes just below their belly button often work well. Ask a baby masseuse or take a look at our guide to baby massage. Bicycle legs is another good one and fun to sing along to.

    Baby diarrhoea


    A lot of newborns go through this as their little digestive systems are still developing even after they are born. Your baby’s poos will probably be relatively runny-looking most days anyway, especially if you are breastfeeding. However, if they’re pooping like a trooper and it’s extremely runny then you might be wondering ‘does my baby have diarrhoea?’ Other signs could be a fever or turning their little noses up at their milk. If there are fewer wet nappies and the pee is strong-smelling when it finally makes an appearance, then they are probably dehydrated.

    What causes it?

    • Viral infections – a rotavirus or a tummy bug is the most common cause
    • Parasites – these can spread when a baby puts something in their mouths that may have come in contact with faecal matter. It sounds grim, but baby groups and nurseries are prime spots for this – it’s very common
    • Lactose intolerance – some babies bodies can’t digest the lactose in milk properly

    What to do if baby has diarrhoea

    Baby diarrhoea leads to dehydration so try and top baby up with fluids more often. Speak to a healthcare professional about what to give and how often.

    If you think your baby’s leaky nappies might be due to lactose intolerance or a milk allergy then speak to your GP, health visitor or a public health nurse. If you’re formula feeding they may suggest a lactose-free milk, or other alternatives to prevent baby diarrhoea. Another solution offered could be lactase enzyme drops which can be added to breast milk or formula – it’s important you get the go-ahead from a medical professional before you switch their milk.

    With all those full nappies your baby’s new bum can get a little irritated so try and whip off the dirty nappies as soon as you can. A warm damp cloth or cotton wool is gentler than wipes. If you can, give their bottom some time to breathe for a few minutes on the changing mat.

    Is there anything else I should look out for?

    If you spot any blood or mucus in your baby’s nappy then talk to their GP right away.


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    Important advice to mothers

    The World Health Organisation (WHO) recommends exclusive breastfeeding for the first 6 months of life. SMA® Nutrition fully supports this and continued breastfeeding, along with the introduction of complementary foods as advised by your healthcare professional.