A newborn's first bowel movement is meconium a greenish-black substance which was in the baby's bowel before the birth. It can be alarming if you're not expecting it, but its appearance shows that all is well with your baby's excretory system.
Breastfed babies' stools smell pleasant. They are usually bright yellow or mustard-coloured and very loose.
Green-coloured stools sometimes mean that bile salts have not been completely re-absorbed. They can show that your baby has colic (see Breastfeeding/what happens in a breastfeed), but sometimes they just happen.
Some breastfeeding mothers see very direct connections between their diet and their baby's nappy contents:
"When I was breastfeeding all I had to do was eat one grape and we would have a terrible runny nappy."
We had onions the other night and this had a noticeable effect on Tommy, our six-week old. He cried a lot during the evening and then produced an unbelievable nappy!"
Bottle-fed babies have light brown, more formed stools.
Babies who are being weaned sometimes produce multi-coloured nappies, often the same shade as what they have just eaten. If you can see that certain foods have passed straight through, leave these out of the diet for a while.
There will be a wide variation in how often your baby fills their nappy. Some do this at or about every feed. Others, particularly those being breastfed, can go for several days - even a week - without having a bowel movement. This is normal.
Quite a few babies may strain or cry when passing a stool and this is also normal. Your baby isn't constipated if the stools are soft.
You will probably notice that your baby's stools will vary a bit from day to day and week to week. However, if you notice a very particular change, such as the stools becoming very smelly, very watery or very hard -particularly if there is blood or mucous in them - then you should talk to your doctor or health visitor.