The Use of Spare Embryos Remaining after In Vitro Fertilization for Research and Therapy
Many embryonic stem cells currently available for research and eventual therapy have been derived from spare embryos remaining at IVF (In Vitro Fertilization) centers. These embryos exist because IVF treatment can result in the development of more of them than are ultimately needed by those attempting to have children. This means that some embryos remain at infertility treatment centers that will never be used for the reproductive purposes of those who had them developed. To understand how and why this occurs, it is important to grasp how the IVF process works. IVF involves joining a human egg and sperm in a laboratory dish where they can fuse to form an embryo. The eggs that figure in this process come from women who have undergone ovarian stimulation and egg extraction. Since women ordinarily develop only one or two mature eggs a month, they are usually advised to improve their chances of pregnancy by increasing the number of eggs they produce. They can do so by injecting themselves with ovulation-stimulating drugs for eight to twelve days.
The use of such drugs poses certain health risks to those receiving them. The multiple eggs produced are then removed from the bodies of these women in a procedure known as ultrasound transvaginal egg retrieval, which also carries certain physical risks for women. Many embryos that are not used for the first IVF round are frozen. Should the initial IVF attempt prove unsuccessful or should patients succeed in a first try and want to have additional children in the future, these frozen embryos would be available to them. The main advantage of such freezing is that there would be no need for women to undergo the risks of egg retrieval again in future IVF attempts. As a result of this practice, it was estimated that in 2002 there were nearly 400,000 frozen embryos stored in the United States.
Those with frozen embryos remaining after IVF treatment may decide that they no longer need them for procreation for a variety of reasons, such as that they now have sufficient children, they no longer have the heart to undergo additional IVF treatments, or they are not able to develop viable embryos. They face a choice of discarding them, donating them to another couple for procreative attempts, donating them for research, or keeping them frozen indefinitely. Some among them choose to donate these spare embryos for research. Others have fresh embryos remaining that they do not plan to use for reproductive purposes in the future and that they do not wish to cryopreserve. They choose not to freeze them for varying reasons, such as that they do not want to use embryos that might be damaged by freezing or that their religious tradition proscribes embryo freezing. Those who choose against cryopreserving spare embryos may also decide to donate them for research.
Some spare embryos remaining at IVF clinics are not considered viable and could not be used in reproductive efforts. Bernard Lo and colleagues point out that ‘‘embryos may be of poor quality or otherwise fail to develop sufficiently for implantation or freezing. In these situations, the IVF embryos cannot be used in ART (assisted reproductive technology).’’ Some couples decide that instead of discarding such embryos they would rather donate them for research that might aid those who are seriously ill. Three of the seventeen new human embryonic stem cell lines derived in 2004 by Douglas Melton and his team at Harvard University were derived from IVF embryos with poor morphological characteristics; these embryos would otherwise have been discarded. Four of them were of ‘‘intermediate’’ quality and would also probably not have been used in attempts at IVF.
Thus there are many reasons why embryos remain at IVF clinics in both frozen and fresh states that will not be used in attempts to have a child. Some who object to the destruction of these embryos in stem cell research maintain that they should be donated to others in order to initiate pregnancies. Yet some couples and individuals do not wish to have such embryos used to create children who would be biologically theirs but who would exist somewhere else in the world, children who would be raised by people about whom they know nothing. For this reason, many among them choose not to donate their spare embryos to others for procreative purposes. Rather than discard these embryos, they decide to donate them for embryonic stem cell research that might help others overcome serious diseases.