I recently stumbled across this article (free, but registration required) by SUNY Albany's Bonnie Steinbock. The paper examines the growing practice of prenatal testing and considers who benefits from such testing for adult-onset conditions (such as breast cancer, schizophrenia, and Huntington's disease).
Steinbock outlines the purposes of prenatal testing in general: (1) prospective parents who are willing to consider abortion may wish to make an informed decision about continuing a pregnancy; (2) prospective parents, including those who would not terminate, may wish to have information available to help them prepare for the birth of a baby with health problems or special needs; (3) society may reduce the prevalence of genetic diseases; or (4) prospective parents may seek testing "for the good of the child."
As Steinbock points out, the predictive value of tests differs (meaning that some tests provide definitive information about whether a person will develop a given condition, as in the case of Huntington's, while others offer much less certainty). Some conditions are preventable or treatable, and others are not (this is the clinical utility piece I've blogged about recently). And even for conditions that are not treatable today, prospective parents might still hold out hope for a future treatment.
Botom line: Steinbock doesn't buy the argument that prenatal genetic testing for untreatable adult-onset diseases can be justified on the grounds that it is for the good of the child. She rejects the wrongful life concept in this context, noting that "in almost cases the child, once born, will have a life worth living. This is so even in the case of severe disability at birth, and much more so in the case of adult-onset disorders." This isn't to say that Steinbock opposes selective abortion--she defends it elsewhere--but justifications other than the benefit of the child must be marshaled to support it.