Updated

A woman has conceived two baby girls 10 days apart.

Kate and Peter Hill, from Brisbane, Australia, only had sex once but an extremely rare medical phenomenon known as ‘superfetation’ means she became pregnant while already expecting.

Kate was diagnosed with polycystic ovarian syndrome, a hormonal condition that left her unable to ovulate, in 2006.

She underwent hormone treatment to spectacular results, falling pregnant twice.

More on this...

It is a medical phenomenon so rare there are only 10 medically documented cases of it in the world.

“Superfetation is extremely rare," Kate said. "I had fallen pregnant and my body had spontaneously released another egg giving the embryos different gestational ages.

“What makes this case even more rare," she continued, "is that my husband and I only had intercourse one time— his sperm stayed alive for 10 days to fertilize the second egg released.”

Click for more from the Sun and Today Tonight.