The number of babies diagnosed with Down syndrome in Britain has risen sharply over the last 20 years largely due to women delaying motherhood, research showed today.
An increase in the number of older mothers is behind a 71 per cent rise in the number of babies with the condition from 1,075 diagnoses in 1989/90 to 1,843 in 2007/8.
However, the number of babies born with Down syndrome has remained fairly static over the same period due to improved screening and subsequent abortions, the study found.
Live births of babies with Down syndrome fell just 1 per cent, from 752 to 743 over the time period.
Experts from the University of London analysed data from the Down syndrome register for England and Wales for the study, published online in the British Medical Journal (BMJ).
The anonymous register holds 26,488 antenatal and postnatal diagnoses of Down syndrome made by all cytogenetic laboratories which analyse chromosomal abnormalities since 1989.
Joan Morris, professor of medical statistics at the University said “what we’re seeing here is a steep rise in pregnancies with Down syndrome but that is being offset by improvements in screening”.
The risk of having a baby with Down’s syndrome is one in 940 for a woman aged 30. But by age 40, the risk rises to one in 85.
The proportion of couples diagnosed with a Down’s syndrome pregnancy who decided to terminate has remained constant at 92 per cent.
The authors concluded “increases in maternal age would have caused a 48 per cent increase in births with Down’s syndrome in the absence of terminations between 1989/91 and 2005/7.
“However, terminations of Down’s syndrome pregnancies due to an increase and improvements in antenatal screening have caused the number of live births with Down’s syndrome to remain constant.”
PA