Last week, I discussed genetic tests that aim to detect disorders in a foetus during pregnancy. This week, I look at pre-pregnancy or carrier tests. These tests are taken by couples that are considering having a baby, but are worried about the genetic disorders that they may pass on, possibly because there is a history of genetic disease in the family. The couple can then base their decision on how to go ahead with family planning on the test results.
There is an overlap between what pre-pregnancy tests do and the services offered by more traditional genetic counselors and clinical geneticists. In fact, most companies market their preconception tests via genetic clinics, rather than directly to consumers. Whether direct-to-consumer genetic tests should be legal at all is still being debated in many countries.
Two companies that develop sequencing-based preconception tests are Good Start Genetics and Ambry. Counsyl, another company in the sector, uses array-based technology. The number of disorders that can currently be detected with pre-pregnancy tests is higher than what is possible with non-invasive prenatal diagnosis. Whilst Sequenom's prenatal test returns information about a single disorder (trisomy 21), Good Start's test diagnoses 22 disorders, Counsyl's over 100, and Ambry's 90. But even once the providers of prenatal tests catch up, there is still the question if it makes sense to screen for less severe conditions. Do parents really want to know that their baby boy will suffer from pattern baldness once he grows up? The number of conditions that can be diagnosed is likely to be different from the number of conditions that are actionable.
But why stop at genetic counselling for couples? The start-up Gmatch plans to offer genotyping to the customers of an online dating website who want their future partner not only to be compatible socially, but to be a perfect genetic match as well.
Next week, I'll look at the third way besides prenatal and pre-pregancy diagnosis: Pre-implantation diagnosis.