Some research suggests that the miscarriage rate following chorionic villus sampling may be as high as 2%, the researchers said, which, if true, would raise that toll closer to 600.

BBC: Down's test miscarriage warning

To confirm or rule it out, a further test is offered - either amniocentesis and chorionic villus sampling, both of which use a fine needle to take tissue or fluid from inside the womb.

BBC: Down's test miscarriage warning

However, the researchers said that despite a lower number of invasive tests, the heavier reliance of this method on chorionic villus sampling earlier in pregnancy could actually mean an increase in the number of healthy babies lost if the miscarriage rate using this method was closer to 2%.

BBC: Down's test miscarriage warning