The condition is called superfetation, and it's so rare, her doctor had to Google it!

charlotte and olivia miracle babies
Credit: Today Tonight

If you think it's safe to have unprotected sex when you're pregnant because,'re already pregnant, this story might give you pause.

After struggling to conceive due to a diagnosis of polycystic ovarian syndrome, which prevented her from ovulating, Australian mom Kate Hill underwent hormone treatment to boost her chances and was happily surprised with a miracle pregnancy. But then, 10 days later, she found out she was pregnant again!

Wait, what?

Here's the deal: While most women don't ovulate once they've got a bun already in the oven, Kate did. The condition even has a name—superfetation—and it's an extremely rare phenomenon in which a woman becomes pregnant while already expecting. It's so uncommon, in fact, that Kate's doctor had to Google it (!!!). Only 10 cases have been recorded in the entire world—so cool!

"We actually didn't realize how special that was until they were born," Kate told Today Tonight. "What makes this case even more rare is that my husband and I only had intercourse one time."

"Hole in one, maybe?" her husband Peter then quipped. Pretty funny. We're glad to see that making medical history hasn't done anything to damper this new dad's sense of humor!

Meanwhile, though the Hill babies were given delivery dates 10 days apart, the sweet little girls—named Charlotte and Olivia—instead arrived together two days before Kate's scheduled C-section last December, both fine and healthy. The non-identical twins measured very differently in size and weight, though.

Now almost a year later, the double miracle babies are happy and healthy and gearing up for their first birthday party, complete with Minnie Mouse-themed invitations. And get this: Despite having their hands full with the demands of raising two daughters, the Hills' haven't yet ruled out having more children. Another hole in one, perhaps?

Hey, miracles happen to those who believe in them, right?

Hollee Actman Becker is a freelance writer, blogger, and a mom. Check out her website for more, and then follow her on Twitter at@holleewoodworld.