Women expecting a baby or planning a pregnancy are being offered a fast-growing array of tests to check if they are carriers for hundreds of mostly rare genetic diseases, as reported in the January 6th issue of the Wall Street Journal.
Such genetic testing, called carrier screening, has long been targeted mainly at people of certain ethnic groups such as Ashkenazi Jews, who are at higher risk for some conditions such as Tay-Sachs disease. Now, companies that offer carrier screening are promoting the idea that testing everyone for many diseases is a more effective way to reduce the number of babies born with serious disorders, including cystic fibrosis, a life-limiting lung condition, and Canavan disease, a fatal neurological disorder.
Carrier screenings mostly look for diseases that can only be passed to the next generation if both parents have the same genetic variation, and that happens very rarely. As many as 1 in 29 Caucasians of European descent are carriers for cystic fibrosis, for example, but just 1 in 3,000 or so newborns has the disease.
Women are usually screened first. If the results are positive, the test is also done on their male partners.
ACOG currently recommends universal carrier screening for just one disease, cystic fibrosis. Based on family history, other tests also might be advisable, including for spinal muscular atrophy, the top genetic cause of infant death, and Fragile X syndrome, the most common inherited type of intellectual disability.
But since these diseases are rare and many people may not be aware of their ethnicity or many be from mixed ethnicities, most fertility specialists are recommending screening for all patients. At RPMG we offer Counsyl’s Next Generation sequencing tests to all patients. If a woman shows up with an abnormal gene, then her partner is tested. If they both have the gene for the same disease they can be offered preimplantation genetic diagnosis (PGD) or if they get pregnant without IVF, prenatal screening of the fetus.
ACOG, in concert with three other medical-professional groups, expects in early 2015 to issue a statement on universal carrier screening to help guide labs and physicians.