Unborn twins caught on video MRI for the first time

They might share the same DNA and cramped living space, but as these images reveal, life is anything but identical for unborn twins.

This unprecedented glimpse into their inner world is afforded through a recently developed form of magnetic resonance imaging (MRI), which is being turned on twins for the first time.

Whereas conventional MRI takes snapshots of thin slices of the body as it penetrates through it, so-called cinematic-MRI takes repeated images of the same slice, then stitches them together to create a video. This means that a moving structure such as a fetus – or several fetuses – can be visualised in unprecedented detail.

"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 the Robert Steiner MR Unit at Imperial College London, who recorded the images.

She has been using the technique to study twin-to-twin transfusion syndrome, a relatively common complication in which the blood supplies of twins sharing the same placenta become connected. As the twin receiving its sibling's blood grows larger, the growth of the donor twin becomes stunted. In the worst cases it can prove fatal to both twins. Fortunately, an operation that involves blocking the shared blood vessels usually saves them, but its impact on brain development is relatively unknown.

Different brain sizes

Taylor-Clarke is using cine-MRI to explore this process in more detail. "Using this technique we can begin to say something about the impact of these two separate environments within a shared environment and how this affects the supposedly genetically identical brain," she says.

Although they have only scanned 24 pairs of twins so far, they are already getting new insights that could help predict future developmental problems. For example, some twins who had undergone the operation and had apparently normal brains when screened using ultrasound showed differences in brain volume when screened using the more sensitive MRI technique.

"These donor twins had smaller brains than their co-twins," says Taylor-Clarke. What's more, those twins with near-identical brain volumes in the uterus seem to do better in terms of their neurodevelopment once they are born than those with a larger difference in brain size.

Ultimately the team hopes to develop a tool that could accurately predict developmental problems in advance of birth, meaning parents could be given extra support once the twins are born.

But this kind of imaging also holds more general lessons for twin development. Although one might assume that identical twins share the same environment until birth, it's clear that they may have had quite different experiences, which may already have left lasting impressions on their development.

Imperial College London is currently recruiting pregnant women who are carrying twins for further imaging studies. If you are interested in being scanned, contact m.taylor-clarke@imperial.ac.uk