With potential pictures like this, how could you miss out on getting a 3d/4d ultrasound?
A crowded womb
By NATASHA PEARLMAN
Twins appear to kiss in the womb
A silicone model of fraternal twins - who have their own placenta and amniotic sac
A twin leans over and kisses the cheek of her sister in a heart-warming picture that would not be out of place in any family home.
Yet these siblings are a not even born and the astonishing images have been captured on a new 'four-dimensional' ultrasound scan of the womb.
• See the stunning 4D scans
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The scans are a highly developed form of traditional ultrasound where very high frequency sound waves are used to produce images of what is inside the body.
As with older forms of ultra-sound, sound waves a emitted from a transducer, or probe, which is placed on the mother's abdomen and then moved to 'look at' areas in the uterus. These sound waves bounce back off the foetus, helping to create a 'picture' of the child on a screen.
The new 4D scan us ses the same frequency of sound waves w as in a normal ultrasound. But the sound waves are directed from many more angles, producing a 'real-time' video of the foetus as it moves and allowing scientists to say the images are in four dimensions.
This advanced technology has allowed scientists to capture the development of foetuses like never before, including twins and triplets jostling for space in the womb while grasping each other's hands and even faces.
The images have also allowed scientists to create life-size silicone models and astonishing computer-generated images of the multiple foetuses, some of which are seen in the pictures shown here.
For the first time, it has also been possible to see detailed pictures of 'vanishing twin syndrome' - where a foetus dies and is re-absorbed into the womb, often in the early stages of pregnancy.
Doctors estimate this occurs in 11 per cent of pregnancies. Some scientists have suggested that 'vanishing twin syndrome' occurs because of a lack of nutrients, so the mother's body naturally 'loses' one or more foetus in order to boost the survival of the others.
Scientists have also been able to examine a variety of twin called a 'mirror' twin, which occasionally occurs when embryos split. This means that while one twin is left-handed, the other is right-handed. But in extreme cases it can lead to one twin having its heart on the left, while the sibling has their heart on the right.
London-based obstetrician Professor Stuart Campbell, who is the pioneer of 4D scans in Britain, performed the scans for a National Geographic documentary.
He says: 'It was fascinating to see the babies in more detail than ever before. I was amazed at the detail in the faces - smiles, blinking - and the interaction between multiple foetuses.'
The scans were used to particular effect when charting the progress of the naturally conceived, identical quadruplets of Julie Carles, 38, whose story was revealed exclusively in the Mail last year.
The scans showed the four fetal bodies developing in minute detail - it is even possible to see their eyelids opening - as well as their developmental patterns as they jostle for space in the womb.