Oct 29, 2009
A rise in older women becoming pregnant has led to a big jump in Down's syndrome diagnoses in Britain, but fewer babies are born with the condition because more than 90% are aborted, researchers said.
Scientists found that diagnoses of Down's syndrome rose by 71% between 1989 and 2008, largely due to a sharp rise in the number of women wanting to become mothers later.
But the number of babies born with Down's fell by one percent because more women were screened and chose to terminate the pregnancy.
"Dramatic changes in demography have been offset by improved medical technology and have resulted in no substantial changes in the birth prevalence of this quite disabling condition," the researchers wrote in the study in the British Medical Journal.
The risk of having a baby with Down's syndrome - which occurs when a child has three copies of chromosome 21 instead of the normal two - increases sharply as women get older.
The risk for a 40-year-old mother is 16 times that for one who is 25.
The researchers from Barts hospital in London and The London Medical School said that without antenatal screening and subsequent abortions, the number of Down's syndrome births would have increased by 48% between 1989 and 2008 due to parents choosing to start families later.
People with Down's often have common physical features such as almond eyes and shorter limbs, and have learning difficulties as well as a higher risk of congenital heart defects and respiratory illnesses.
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