It is estimated that seven percent of married American couples where the wife is of childbearing age are infertile. Many reproductive technologies attempt to bypass infertility by surgically removing eggs and combining them with sperm. The basic form of this technology is called in vitro fertilization (IVF). This procedure combines eggs and sperm in a laboratory dish filled with a culture medium to facilitate fertilization. After approximately forty-eight hours in the dish, several embryos are transferred into the reproductive tract of the women in order to increase the chances of implantation by an embryo. In order to have a sufficient number of embryos for future IVF cycles if needed, more embryos are engendered than are transferred. The remaining embryos are frozen for future use. This practice of freezing human embryos has resulted in hundreds of thousands of frozen embryos worldwide.
This is the central moral criterion in Catholic teaching for evaluating reproductive technologies: If the procedure replaces the conjugal act between spouses it is morally unacceptable; but if it assists the performance of the act or assists the act to reach its natural end, then it can be morally acceptable. What must be preserved is the connection between the unitive and procreative aspects of the spouses’ marital act. Another grave moral problem with IVF and other procedures that incorporate IVF, is the fact that human embryos are routinely discarded or given over to research for destruction. The freezing of embryos also disrespects their human dignity.
IVF is not considered morally unacceptable in Catholic teaching because it is an artificial technique, but because it eliminates the conjugal act and the conjugal love between husband and wife in the engendering a child, who should be the fruit of their act.
The Gospel of Life (n. 14)
Catechism of the Catholic Church (ns. 2373–2379)
New Vatican document on Bio-Ethics (Instruction Dignitatis Personae on Certain Bio-Ethics Questions)