(CBS) Talk about a surprise. Kim Nelson went to the hospital with stomach pains, only to discover she was about to give birth.
"I was 39 weeks and didn't have the slightest clue," the Portland, Ore. woman told the city's NBC affiliate, KGW.
Nelson thought her appendix had burst, prompting her trip to the hospital. Pregnancy wasn't on her mind because she wasn't experiencing morning sickness, and the mother-of-two thought her weight gain was a result of other factors.
"I thought the weight gain was due to cysts I had in my ovaries and working at Dairy Queen and eating all that food," she said. "I didn't have the slightest idea that this little bundle of joy was in my tummy."
When doctors shared the news, Nelson thought they were pulling her leg. Even family members didn't believe it. But four hours later, 7-pound,12-ounce Paige Lynn Dawn Anderson was born. Although Nelson had had no prenatal care, Paige was born healthy, doctors said.
How did this woman not know she was pregnant? Well, she's certainly not the only one.
A TLC reality show called "I Didn't Know I Was Pregnant," has been on air for four seasons. The show reenacts women who don't realize they're pregnant until they go into labor, often in unique places.
Just how common are these situations?
"It's pretty rare that people go through an entire pregnancy and don't realize it," Dr. Jennifer Wu, an OBGYN at Lennox Hill Hospital in New York City, told CBS News.
Wu, who was not involved in Nelson's care, said that's simply because most women menstruate every month. "If they go nine months, that's usually a clue they might be pregnant," she said.
According to Wu, reasons a woman might not realize she is pregnant include young age and irregular periods - or, conversely, old age and potential menopause. Other factors include having no similar signs to previous pregnancies, or plain denial.
Wouldn't Mom feel the baby moving around? Not necessarily, if the placenta is in front of the baby, Wu said.
Wu offers take-home advice to women so they don't find themselves in this situation. "If you have irregular mensies, you should see your doctor," she said. "It's a medical problem."