British study: With older mothers, more Down syndrome has been diagnosed in pregnancies in the past 20 years, but fewer babies born

From The Guardian in the UK:

The number of Down's syndrome diagnoses has risen steeply over the past two decades as women have postponed having families and become pregnant at a later age, but fewer babies with the condition are being born as most opt for terminations, research shows.

In 1989/90, there were 1,075 diagnoses of Down's syndrome in England and Wales, including children born with the condition as well as cases detected in the womb through screening tests.

But by 2007/08, diagnoses had risen by 71% to 1,843, according to a paper published today online by the British Medical Journal. Maternal age is a major known risk factor for Down's syndrome, which is why in the past women were screened from the age of 37. Now, testing is offered to all.

The researchers, from Barts and the London School of Medicine, say they can be confident of the figures because all cases are notified to the National Down Syndrome Cytogenetic Register (NDSCR), which was set up in January 1989.

Two significant changes occurred over that time, say the researchers: better diagnostic tests became available and the age at which women got pregnant rose. Although more cases of Down's syndrome have been detected, fewer children with the condition have been born. The numbers have dropped by 1%, from 752 in 1989/90 to 743 in 2007/8. Around 92% of women who were screened and got a Down's syndrome diagnosis decided to have a termination.

Without terminations, the rise in the age of women becoming pregnant would have led to a rise of 48% in the numbers of births of children with Down's syndrome, the paper says.

It is striking, the authors say, that only 70% of women with a Downs' syndrome baby were screened. This suggests, they say, that even with better tests, "a considerable proportion of women may still decide not to be screened". Research is needed to find out why, they say. The fear that testing may lead to miscarriage could be laid to rest by non-invasive tests in the future.

Parents who choose not to terminate tend to be older than in the past, says the study, which has implications for planning the care of the children. "Moreover, such care will need to be extended as life expectancy is probably rising faster in individuals with Down's syndrome than in others," the paper says. "These concerns might be mitigated somewhat by the much improved educational attainment and social acceptance of people with Down's syndrome."