Hmm my baby sometimes has it and I really think it was pee. Unless you are using pants type diaper as they are very tight. My baby loves to kick so if he wears tape type we will spot wet clothes on his back as the diaper will get loosen. Sometimes their pee are odourless and not necessary coloured.
me too! it happened the first few months.. whenever this happened, i'll just wipe his body using cloth with warm water and change his clothes n diapers..