So: today's news reports that the first "cancer-free" baby has been born.
"What's this?" you ask. "Isn't it awfully rare for babies to have cancer?" Yep. Especially breast cancer, which is more common in older women. But the genetic test to identify known breast-cancer-causing mutations has been around for some time. Now, for the first time, it has been used as a prenatal test--technically, in this case, through preimplantation genetic diagnosis (PGD), which is testing embryos conceived through IVF prior to their being implanted in the uterus.
Certain rare BRCA mutations greatly increase a woman's risk of breast cancer and ovarian cancer--so much so that some women with these mutations decide on prophylactic surgery to remove their breasts and ovaries. However, because these really bad mutations are rare, experts recommend that only women with a strong family history of breast cancer pursue testing. The news story doesn't say whether the couple had such concerns, though presumably this is the case.
Stories like this one don't help the general public understand what genetic testing can and can't do. Even BRCA results are probabilistic: not everyone who has a positive result will go on to develop breast cancer. And there are prophylactic and curative treatments available for breast cancer (though they are, obviously, pretty awful). And who knows what the state of medicine and oncology will be by the time the BRCA mutation carrier born today is old enough to worry about breast cancer?
The opposite set of concerns plays in here too; the fact that this fetus happens not to have any of the mutations that have been shown to increase breast cancer risk does not guarantee that she won't get breast cancer anyway -- presumably there are causal factors we don't know anything about yet, since the vast majority of breast cancer is not due to one of these familial syndromes -- or any of the other zillions of cancers that afflict humankind. "Cancer-free" may be a misnomer in this case.
And finally, isn't there a morally relevant difference between choosing to terminate a pregnancy because of a positive diagnostic result (eg, Tay-Sachs, Down syndrome) and choosing to do so based on a measure of susceptibility? And no hate mail please: I don't mean to imply that the former sort of case is necessarily the right thing to do...only that some such choices might be more easily justified than others.