Short answer. Yes, if the child has already been conceived. Civil Code Article 742 allows donations to conceived and unborn children, accepted on their behalf by whoever would legally represent them once born. A donation aimed at a grandchild who has not even been conceived yet has no beneficiary the law recognizes.
What the law says
Donations made to conceived and unborn children may be accepted by those persons who would legally represent them if they were already born.
Civil Code, Article 742 — Donations To Unborn Children. Read the full provision →
Conceived, not merely hoped for
Article 742 speaks specifically of “conceived and unborn children,” which means the law is recognizing a child who already exists biologically, before birth, rather than a grandchild your son or daughter might have someday. That distinction matters: a donation naming a future descendant in the abstract, with no pregnancy yet underway, is not what this article contemplates, because there is no conceived person yet for the donation to attach to.
Someone else has to accept on the child's behalf
An unborn child obviously cannot sign an acceptance. Article 742 solves that by letting the donation be “accepted by those persons who would legally represent them if they were already born” — typically the expectant parent, standing in for the child in advance of birth the way they would once the child arrives. That representative accepts the donation now, on the understanding that it is being made for the child who is on the way.
What happens if the child is never born
Acceptance on behalf of a conceived child is provisional in a real sense, because the donation is ultimately for that child, and a donation needs an actual person to take effect for. If the pregnancy does not result in a live birth, there is no child for the donation to have been made to, and the property does not vest the way it would have if the birth had gone forward. This is part of why the timing — conception having already occurred — matters as much as it does.
The practical path if the grandchild is not yet conceived
If you want to provide for a grandchild who does not exist yet, even in utero, Article 742 does not offer a route to donate to that child directly today. What you retain is control over your own property in the meantime, and the option of making the donation once the child has actually been conceived, or of arranging the transfer through other means available under the law for property you intend future descendants to receive.
Both sides still need to be alive when acceptance happens
A donation to a conceived child does not fully escape the ordinary rule that acceptance must occur while donor and donee are both living. If the donor dies before the representative accepts on the unborn child's behalf, there is no donor left to have made a completed donation to; the arrangement does not simply carry over as though nothing changed. This is a separate risk from the child never being born, and it is why a donation meant for a grandchild already on the way should not be left unaccepted for long.