Baby poo changes a lot. Feeding is one of the biggest reasons.
Breast milk, formula, mixed feeding and first solid foods can all change colour, consistency, smell and frequency. That does not mean feeding choices are good or bad based on a nappy. It means nappies can give useful context, especially when something changes.
This guide is for observation, not feeding advice. Do not change formula, remove foods, or start a special diet without professional advice.
The first few days: meconium
Your baby’s first poo is called meconium. It is usually sticky and black-green, and NHS-linked baby poo guidance says it commonly appears within the first 24 to 48 hours.
Over the next few days, nappies usually move towards green, then yellow or mustard as milk feeding becomes established.
If you are worried about feeding, wet nappies/diapers, jaundice, or whether your baby has passed meconium, contact your midwife, health visitor, GP or doctor.
Breastfed baby poo
Breastfed baby poo is often:
- yellow or mustard
- loose or runny
- sometimes seedy or grainy
- not very smelly
In the early weeks, breastfed babies may poo often. After around six weeks, the pattern may change and some babies poo less frequently. Pattern matters more than comparing your baby with someone else’s baby.
Log what is normal for your baby so you can see when something is truly different.
Formula-fed baby poo
Formula-fed baby poo is often:
- darker than breastfed poo
- firmer
- smellier
- sometimes greenish, depending on the formula
Some formulas can make poo dark green. Switching from breastfeeding to formula can also make poo darker.
If you are concerned about constipation, diarrhoea, feeding, or whether a formula suits your baby, speak to a health visitor, GP, doctor or paediatrician before making changes.
Mixed feeding
Mixed feeding can make nappies harder to categorise because your baby is getting more than one type of feed.
It can help to log:
- breastfeeds
- bottle feeds
- expressed milk
- formula type if relevant
- rough amount in ounces or millilitres
- stool colour and consistency
- symptoms such as discomfort, vomiting, wind or poor feeding
You do not need perfect measurements every time. “Small bottle”, “left half”, “long breastfeed” or “usual bedtime feed” can still be useful.
Starting solids
When solids begin, poo often becomes:
- thicker
- browner or more varied in colour
- smellier
- affected by visible food colours
You might see orange after carrots, red after beetroot, green after spinach, or little pieces of undigested food. If you are unsure whether red is food or blood, ask a healthcare professional.
First foods can also change frequency. Some babies become a little constipated when solids begin, while others have looser nappies during transitions.
What to record during feeding changes
During a feeding transition, try logging just enough:
| Feed or food | Nappy detail | Useful note |
|---|---|---|
| Formula bottle, 4 oz / 120 ml | Dark green, soft | Baby settled afterwards |
| Breastfeed and banana puree | Yellow-brown, thicker | First week of solids |
| Mixed feed before bed | No dirty nappy | Wet nappies normal |
The goal is to notice patterns over time, not to judge every feed.
When to ask for advice
Speak to a health visitor, GP, doctor or paediatrician if:
- poo becomes very watery, very smelly or pale
- poo is red, white, grey, or black after the meconium phase
- your baby seems unwell, feverish, very sleepy, dehydrated or is feeding poorly
- poo is repeatedly hard or difficult to pass
- you feel worried about feeding, growth, nappies or hydration
How Acornio helps
Acornio helps you keep food or feed notes, stool or nappy observations, symptoms and notes together in one timeline. That can be especially useful during transitions: breast to formula, formula changes, or introducing solids.
It does not tell you what caused a change. It helps you hold onto the details so you can discuss them clearly with a professional if needed.