With everything that could go wrong during a pregnancy, it’s incredible that so many babies are born completely healthy…especially twins.

It’s hard to imagine living in that cramped, watery world for nine whole months but we all do it, and it’s a fascinating thing to see captured on video. A rare look at twins fighting for shared space has been captured during an MRI designed to test for a condition which occurs in identical twins and can lead to one fetus absorbing the blood of the other, leading to dangerous or even fatal side effects.

For most mothers, it’s probably easy to imagine the acrobatics that go on inside the womb; any woman who has ever sat and watched her belly move like there’s an Alien about to pop out of it knows that movement for a fetus is tricky at times. When two of them are sharing that small space, sometimes a small battle for territory must be waged.