Trish Staine thought the back pain she experienced was due to the long run she completed over the weekend.

Training for a half marathon, the 33-year-old Staine ran for two hours and covered at least nine miles on Sunday. Some of her workout included running up and around hills near Duluth, Minn. But when the pain did not subside, Staine finally decided she wanted to go to the hospital.

And good thing she did, because as it turns out, Staine was pregnant.

Upon examining Staine, doctors in the emergency room at Essentia Health St. Mary's Medical Center detected a fetal heartbeat.

"I was like, 'No no no. There's no way I'm pregnant,'" Staine recalled. "But they rushed me up to the Birthing Center, and five minutes after I got into my room, she was born."

The baby arrived five weeks ahead of what would have been the projected due date.

Not only did Staine say she never felt any of the warning signs of pregnancy, her husband, John, had gotten a vasectomy. John even thought Trish had lost weight as she trained for a half-marathon on June 22.

“I just didn't have anything to say,” John said. "It takes a lot to shock me."

The Staines have two foster children and two biological children, ages 7 and 11. Trish is also the stepmother to John's three sons, ages 17, 19 and 20.

The Staines named their daughter Mira, short for "Miracle."

(H/T to Deadspin)