How long will a 10 mg hydrocodone stay in my unborn baby's urine?

Clears you in 72 hrs: Neonatal urine drug testing has been seen as problematic - other means are also not 100%, but favored. A one time small use will almost certainly be gone. And, if legally prescribed, you're not even likely to risk birth defects. That perhaps should be your big concern if your baby's well-being is the issue. Don't abuse drugs - know risks before use - I hope your birthing goes well!