Some of mankind’s most devastating inherited diseases appear to be declining, and a few have nearly disappeared, because more people are using genetic testing to decide whether to have children.
Births of babies with cystic fibrosis, Tay-Sachs and other, less-familiar disorders have dropped since testing came into wider use, The Associated Press found from a review of studies and interviews with geneticists and other experts.
Many of these diseases are little known, and few statistics are kept. But their effects — ranging from blood disorders to muscle decline — can be disabling and often fatal during childhood.
Now, more women are being tested as part of routine prenatal care, and many end pregnancies when diseases are found. One study in California found that prenatal screening reduced by half the number of babies born with the severest form of cystic fibrosis because many parents chose abortion.
More couples with no family history of inherited diseases are getting tested before starting families to see if they carry mutations that put a baby at risk. And a growing number are screening embryos and using only those without problem genes.
The cost of testing is falling, and the number of companies offering it is rising. A 2008 federal law banning gene-based discrimination by insurers and employers has eased fears.
Although genetic testing can raise moral dilemmas, at least one conservative religious group — Orthodox Jews — has found ethically acceptable ways to use it to lessen diseases that have plagued its populations.
“I am a Holocaust survivor. I was born in the middle of the second World War. I hope that I am not a suspect for practicing eugenics. We are trying to have healthy children,” said Rabbi Josef Ekstein of New York, who founded a group that tests couples and discourages matches when both carry problem genes.
Some diseases — sickle cell, cystic fibrosis, Tay-Sachs, thalassemia, spinal muscle atrophy — occur when people inherit two bad genes, one from each parent. The genes can pass quietly for generations until two carriers mate; then children have a one-in-four chance of getting the disease.
(Down syndrome is the best-known disorder for which prenatal testing has long been available, but it’s caused by an extra chromosome during abnormal cell division — not genes inherited from the parents.)
Statistics for inherited diseases are hard to come by — birth certificates often don’t list them, and they sometimes aren’t diagnosed for months or years after birth. Yet, there’s little doubt that testing has put a dent in many.
“We’re definitely seeing decreased rates of certain genetic disorders as a result of carrier screening,” said Dr. Wendy Chung, clinical genetics chief at Columbia University.
In five years, she has seen only one case of Tay-Sachs, a neurological disease that used to be more common in Ashkenazi, or Eastern European Jews.
