SURPRISE DELIVERY: Woman gives birth to unexpected 10-lb baby girl

A Massachusetts woman gets the surprise of her life.

Katie Kropas was rushed to the hospital on Tuesday morning with lower back pain.

Three days later she's preparing to go home with a new baby.

The instant mom was shocked because she says she didn't know she was pregnant.

"I thought I had put on...like some Christmas season weight, you know, but I never thought I was pregnant, never," said Kropas.

Doctors say it's called a "cryptic" pregnancy."

They say it happens more often than you think, especially if the woman is overweight or has irregular periods.

It's even the subject of a show on TLC called "I Didn't Know I Was Pregnant."