Some will be retrieved if pregnancy and birth attempts fail or if parents decide they want to add another born child to their family. However, many of the so-called “spare” embryos will remain in storage, to be donated to an infertile couple or to science; many will ultimately be destroyed.

Although there are no precise numbers, researchers estimate that there are currently hundreds of thousands of embryonic human beings stored in fertility clinics throughout North America and Europe. In Canada, because legislation prohibits the creation of new embryonic humans for anything beyond reproductive purposes (which can include supportive research), the so-called “spare” embryos — embryonic human persons already in existence but unwanted — are especially vulnerable. Not protected by stringent guidelines normally governing research involving human subjects, they may be used in experiments that could result in their death and destruction.

Given this grim picture, many Catholics wonder if it would be right to attempt to “adopt” or “rescue” these so-called “spare” embryos. Even in pro-life circles, where there is absolute agreement on the worth and dignity of these young human persons, embryo adoption or rescue is a very contentious issue.

On the one hand, adoption or rescue involves techniques that are prohibited by Donum Vitae, the prophetic document published in 1987. To be adopted or rescued means that the embryonic humans must be thawed, then transferred to the womb of the (presumably) adopting mother. However, Donum Vitae prohibits embryo transfer (ET) and surrogacy as being inconsistent with the respect we should have for all human life.

Advocates of embryo adoption or rescue counter that Donum Vitae addressed questions of assisted human reproduction and may not have been anticipating the tragedy of these abandoned embryonic humans. They make the case that the prohibitions in Donum Vitae might not apply to altruistic acts of adoption or rescue which could be regarded as corporeal works of mercy. The woman carrying the child is not a surrogate mother, in this view, but the adoptive mother providing the care needed if the child is to be born.

Even if adoption or rescue does not result in the birth of a child (and chances are that it will not), the couple will still have freed the embryonic child from the child’s frozen state and will have provided the child with the intimate, kinetic connection of a nourishing womb. No matter how fleeting the relationship, the embryonic human will have had parents who loved this child very much.

On the other hand, as altruistic as they may be, embryo adoption and rescue carry their own moral dangers. There is the possibility of co-operation in an evil act. Couples suffering from infertility and who themselves would not engage in IVF might turn to embryo adoption as a way of providing them with the opportunity to experience pregnancy and child birth in a way that conventional adoption does not. At the same time, it might ease the conscience of couples considering IVF to know that there are adoptive parents for any “spare” embryos that might be created.

More troubling to me is the selection process that might be used in deciding which embryonic human persons are to be transferred. What criteria will be used? How will prospective parents choose the embryonic children they hope to adopt? Will these very young persons, already subjected to the indignity of IVF, be required to undergo preimplantation diagnosis? Will embryonic humans be chosen for transfer based on particular genetic traits desired by the prospective parents? Even if a very common sense approach is used and the embryos who are most likely to survive are transferred, a further underclass of the most marginalized human population will be created: those “spare” embryos unfit for transfer.

Finally, there is the danger of the slippery slope which, in embryo adoption or rescue, is very slick indeed. It may be one thing for couples committed to raising the child to engage in embryo adoption or rescue. Would it be permissible for single women to undertake this rescue work? Would it be permissible for a woman to undergo embryo transfer and then have another couple raise the child? Could a couple unable to gestate and raise the child themselves pay another woman to do it for them and so partake in the rescue of embryonic humans at least indirectly? Clearly the issue requires very sharp moral crampons and careful footwork if we are to avoid tumbling down the steep and slippery incline into surrogacy, commercialization of the rescue or adoption process, and commodification of these very young human persons.

This said, Donum Vitae is very clear that, no matter how they came into existence, embryonic human beings are to be treated with the same respect and be regarded as having the same dignity as any other human being. It is possible that the church will provide a more nuanced teaching on the question of adopting or rescuing these young human persons whose life journeys have been interrupted. In the meantime, we must remember that, as they are, these embryonic human persons are members of our human community and, as they are, they are known and loved by God. Finally, we must not underestimate what these frozen and suspended embryonic human beings may be doing for us: through their very existence they may be actively working for our salvation in ways that we may only know later.

(Dr. Campion is a bioethicist and researcher at the Canadian Catholic Bioethics Institute in Toronto.)