IN VITRO FERTILIZATION

(IVF) also called test-tube conception medical procedure in which mature egg cells are removed from a woman, fertilized with male sperm outside the body, and inserted into the uterus of the same or another woman for normal gestation. Although in vitro fertilization with reimplantation of fertilized eggs (ova) has long been widely used in animal breeding, the first successful birth of a human child from in vitro fertilization, carried out by Patrick Steptoe and R.G. Edwards of Britain, did not take place until 1978. In vitro fertilization is generally undertaken only after an exhaustive evaluation of infertility has been made. A number of the candidates for IVF are women who suffer from blocked or absent fallopian tubes; others are men with low sperm counts or couples whose infertility is unexplained. IVF procedure includes the recovery (by needle aspiration) of mature eggs and the incubation of the eggs in a culture medium, as well as the collection and preparation of sperm and its addition to the medium. Fertilization generally occurs within 12 to 48 hours. The potential embryo is then placed in a growth medium, where it is observed periodically for division into two-cell, four-cell, and eight-cell stages. During this period the mother receives progesterone to prepare her uterine lining for implantation of the embryo. The embryo, which at this point is known as a blastocyst, is introduced through the cervix into the uterus, in which the blastocyst seems to float free for about three-and-a-half days. If the procedure is successful, the embryo implants itself in the uterine wall, and pregnancy begins. Of the problems that have been noted in IVF procedure, successful implantation seems to be the weakest link. One possible explanation for this problem is that the in vitro zygote develops at a slower rate than the embryo in vivo (i.e., within the body), and hence, the growth of the in vitro zygote and the development of the endometrial tissue are not perfectly synchronized. In vitro fertilization has been a source of moral, ethical, and religious controversy since its development. Although members of all religious groups can be found on both sides of the issues, the major opposition has come from the Roman Catholic church, which in 1987 issued a doctrinal statement opposing IVF on three grounds: the destruction of human embryos not used for implantation; the possibility of in vitro fertilization by a donor other than the husband, thus removing reproduction from the marital context; and the severing of an essential connection between the conjugal act and procreation. Other ethical questions raised more generally have involved the fear of experimentation with human fetuses. Related techniques, such as the freezing of eggs, sperm, or embryos for future implantation, have also raised a number of as yet unresolved moral issues.