A British woman found out she was having a second baby while she was already pregnant and it threw her docs for a loop.

No, this wasn't the case of a missing twin. This was literally a child who had been conceived three weeks after the first.

Rebecca Roberts and her partner Rhys Weaver were a bit confused after they went to her second ultrasound appointment and found out they were having twins.

The second baby had seemingly been immaculately conceived, but was significantly less developed than the first.

"This is not supposed to happen at all, especially in humans," said Rebecca.

Doctors were initially worried, but determined the second child wasn't a twin at all – it was a case of "superfetation," which is a hilarious word that means getting pregnant while pregnant.

A woman's body typically releases hormones and closes the cervix to keep such preg-ception from occurring, but that didn't happen in this case.

It's one of only a few times this has ever been recorded.

Rebecca had to be induced at 33 weeks and he babies were put in intensive care, but they were able to go home around Christmas last year.

Because you're mostly only here for the photos, here are the two little cuties, Noah and Rosalie:

(From IG)