An Australian woman says she has given birth to twins conceived ten days apart.
Kate Hill had previously been told she may never become pregnant because she suffered from polycystic ovarian syndrome, which meant she was not ovulating.
But after receiving hormone treatment for the condition not only did Mrs Hill manage to conceive, but she apparently conceived twins at different times.
According to reports Mrs Hill and her husband Peter succesfully conceived and then ten days later conceived again, despite having had unprotected sex only once in that period.
It is very rare for a woman to conceive a second time while already pregnant.
Most twins are the result of the woman releasing two eggs at the same time, or occasionally, if a fertilised egg splits.
Mrs Hill, however, released another egg after conceiving which then fertilised and implanted in the womb to develop into a separate healthy foetus.
Only ten cases of this medical phenomenon, known as superfetation, have been recorded around the world.
The non-identical twin girls, Charlotte and Olivia, were born with different weights, blood types and gestational development.
They are now 10 months old.
Mrs Hill told Australian television: “We actually did not realise how special that (form of conception) was until they were born.
“What makes this case even more rare, is that my husband and I only had intercourse one time – his sperm stayed alive for 10 days to fertilise the second egg released.”
Commenting on the rare conception, Mr Hill joked: “Hole in one, maybe.”
