An infant dubbed the "Christmas baby" was born on a subway train in the US city of Philadelphia when his mother suddenly went into labour.
Two transit police officers were called in and helped deliver the baby after the woman's waters broke.
The mother and child were immediately taken to hospital and are doing well.
Police Sergeant Daniel Caban told NBC TV he had been hoping for a quiet day at work but the baby's arrival had been "just a blessing".
The chief executive of Philadelphia's public transport system tweeted that the baby's fare had been waived.