Have you ever wondered why your baby often pees the moment the nappy is taken off?  I remember how I always held a nappy underneath my baby’s bottom at baby clinic when I carried my baby between the changing mat and the weighing scales.    I also remember how my babies/toddlers waited until they had a clean nappy on to do a number two.  I may have finally found out the answer.  No scientific proof you understand?  This evidence is purely anecdotal, but something to be aware of.
Earlier this month I attended a Natural Infant Hygiene (NIH) session at Nappy Ever After where I heard why the session leader started baby-led pottying, otherwise known as Elimination Communicaton (EC) with her daughter.   At about 3 months old, her baby hadn’t done a number two for a few days.  This was followed by a massive poo explosion. 
The thought occurred to the mother that ‘elimination’ couldn’t happen or was difficult while her baby was lying down in a nappy.  She offered her baby a pot and there was no more ‘constipation’ after that.   Gravity and exposure to the air seemed to help stimulate ‘elimination’.
As parents, we have been told that we should just leave babies/toddlers in nappies 24/7 so the poo and pee just comes out of the child ‘naturally’.  Indeed we have been warned that giving your baby the opportunity to poo on a pot from an early age can be dangerous leading to ‘holding’ ie constipation.  See link to Huffington Post article below.  
This mother’s experience implies that babies do hold, that they are born with the instinct or if not, develop the desire quite early on to keep themselves clean and dry.  But when we don’t give them the opportunity to poo (and pee) on a pot they give up.  Then when we try to ‘teach’ them to try to control their bowels at around 2 years old it’s a problem. 
And it is a problem.  We are hearing about more and more 4 year olds who are dry during the day but ask to put on a nappy to do a poo.   

Read an article on the opposite point of view in the Huffington Post.  Steve Hodges: A Doctor’s Response:  Don’t Potty Train Your Baby.  At Real Nappies for London we are sharing this knowledge.  It’s up to you to decide what works for you and your baby.