It's not the first time twins have been filmed before inside the womb. It is the first time they can be seen in such detail, given the film was made using images taken from MRI.
New Scientist states that magnetic resonance imaging takes photos of "thin slices of the body" repetitively and "stitches them together" to create such a detailed video:
"A lot of the so-called videos in the womb are very processed, so they do a lot of reconstructing and computer work afterwards. These are the raw images that are acquired immediately," says Marisa Taylor-Clarke of theRobert Steiner MR Unit at Imperial College London, who recorded the images.
See how clear the images and movement of the twins are for yourself:
New Scientist states Taylor-Clarke is using this technique to study a fairly common complication among twins where their blood supply becomes connected. As you can see in the video, one of the twins is clearly larger, as it is receiving more of the blood supply.
Taylor-Clarke, more specifically, is researching the consequences of the operation performed to stop the shared blood supply.
Taylor-Clarke's research is still ongoing, but beyond the main objective of the project, it is also revealing so much more that could be used to predict complications before birth and about twin development in general. The research has already begun to show that even though they are genetically identical and in the same environment, they have different experiences while in the womb that can impact their development.