Amazingly, this is the face of a foetus aged just 17 weeks old.
Professor Stuart Campbell, who took the picture at his London clinic with 3-D and 4-D scanning equipment, said it did not necessarily show the unborn child had feelings - but it was certainly displaying human behaviour.
'This is a joyful expression of the humanity of the foetus. I have seen a foetus making a crying face at around 18 or 19 weeks, but not a nice smile.
'This is the earliest on record - it is just a delight.'
Professor Campbell, former head of obstetrics and gynaecology at King's College and St George's hospitals in London, said he did not know what caused the smile.
'It is part of a sequence that involves yawning and making breathing movements and opening its eyelids and, of course, it makes a crying face.'
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