Is pre-implantation genetic diagnosis (PGD) acceptable for Catholics?

The official position of the Catholic Magisterium on prenatal diagnosis has been articulated in the instruction on Respect for Human Life in Its Origin and on the Dignity of Procreation (Donum Vitae) issued by the Congregation for the Doctrine of the Faith (CDF). In that document it has been stated that prenatal diagnosis is “ permissible if the methods used, with the consent of the parents who have been adequately instructed, safeguard the life and integrity of the embryo and its mother and does not subject them to disproportionate risks. But this diagnosis is gravely opposed to the moral law when it is done with the thought of possibly inducing an abortion depending upon the result…”.

Although the document does not address explicitly the moral acceptability of pre-implantation genetic diagnosis (PDG) it is reasonable to infer that genetic testing performed on early, pre-implantation embryos obtained by uterine lavage with the aim to identify a suspect genetic abnormality and eventually to correct it through somatic gene therapy is morally licit. PGD can be performed either through noninvasive blastocyst culture or by splitting the 4 to 8 cell embryo in two. By virtue of the totipotency of the embryonic cells even the implantation of a ‘half’ of the embryo can develop into a whole individual. Unfortunately, this diagnostic technique has been increasingly used as a means of selecting those embryos carrying genetic abnormalities and eliminating them.  In that case PDG is manifestly contrary to the respect of every human life from the very moment of conception defended by the Catholic Magisterium and, thus, morally unacceptable.