Sonia Banks, 22, and her partner, Allan Stanley, 21, went to the hospital after Banks' water broke Thursday afternoon, The Daily Telegraph reported.
But midwives at the hospital sent her and Stanley home, telling them that the baby wouldn't be born for a long time, The Telegraph said.
The pair left the hospital and boarded a train from London to to Maidstone, The Telegraph said. They were on the train Thursday for just seven minutes when Banks realized she was having contractions.
A midwife from the hospital and a police officer assisted in the birth and Banks' daughter, Phoebe, was born without any complications, The Telegraph reported.
The train was delayed for 37 minutes due to the birth.