London doctors have captured what appears to be twins battling for space in their mother's womb.
An MRI machine recorded the battle during a study on a potentially deadly condition called twin-to-twin transfusion syndrome.
The condition in which blood from one twin moves into the other only occurs in identical twins and can lead to one child being born much smaller than the other.
In the video, the smaller twin looks cramped and repeatedly kicks out at its sibling with both feet.
The other twin responds to the blows by arching its back and pushing its knees out.