Those who consider embryo adoption/rescue a licit means to save the lives of cryopreserved and abandoned embryos often have recourse to an analogy between gestation and wet nursing, claiming that since procreation is complete at the moment of conception, there is no moral difference between gestating another person's child and wet nursing another person's child. The claim that procreation terminates at conception is evaluated in light of the thought of St. Thomas, and a determination of the moral means of ordering oneself to the good of the species by means of procreation is made in accordance with the natural law reasoning advocated by that saint. Summary: The Catholic Church teaches that procreation must be the fruit of the marriage act. Some moral theologians consider procreation to be complete at the moment of conception and so conclude that the impregnation of a woman by means of embryo transfer does not violate the principle that procreation must be the fruit of marriage. Others, however, consider procreation to include gestation and birth. This article advances reasons why the latter view should be preferred and what this entails for the ethics of embryo adoption or rescue.
Keywords: St. Thomas Aquinas; embryo adoption; embryo rescue; embryo transfer; natural law; sexual ethics.