In Dignitas Personae it is stated that gene therapy to correct genetic abnormalities is morally licit if it is purely to restore normal gene functioning. The modifications could be done in utero or after birth as long as the modifications did not pose undue risk to the person.
As I understand the modifications in the article, it would be morally illicit because it would be done as part of in vitro fertilization.
The portion from DP most directly related would be the second paragraph of section 26 which reads:
The moral evaluation of germ line cell therapy is different. Whatever genetic modifications are effected on the germ cells of a person will be transmitted to any potential offspring. Because the risks connected to any genetic manipulation are considerable and as yet not fully controllable, in the present state of research, it is not morally permissible to act in a way that may cause possible harm to the resulting progeny. In the hypothesis of gene therapy on the embryo, it needs to be added that this only takes place in the context of in vitro fertilization and thus runs up against all the ethical objections to such procedures. For these reasons, therefore, it must be stated that, in its current state, germ line cell therapy in all its forms is morally illicit.