That is exactly why they stank, and that is not how they should be at all. If they are mec stained then that is a problem, hence why you should contact your care provider if they break and there is an odour.
The mec can indicate fetal distress, and also poses serious risk to bubs if aspirated, it can be fatal for them.
Ah, I was wondering why other people thought I was strange when I said mine had a bad smell! I knew about the whole mec = fetal distress thing, so we went off to the hospital immediately. Luckily baby was absolutely fine. Mum was concerned about the amount of blood though, there was ALOT. They never explained why though.