Piss is piss....whether it be a baby, adult, man, or woman. Just make sure that your baby is not on any medications as this can lead to false positives or raise suspicion. You're probably better off subbing someone elses clean piss because it'll be kinda hard waiting for your baby to use the bathroom, at least with an adult you know when they have to go and you know they wont make a mess. Just make sure to practice subbing with regular tap water several times to check if the temp will stay accurare, if you substitute is below temp. you will almost always fail or raise serious suspicion. Make sure its between 92-100 degrees when you submit the sample.