—when the wife is infertile because the canal that links her ovary to her uterus—the Fallopian tube—is blocked.

Fourth technique: external fertilization is performed in a test tube between a sperm sample taken from the husband and an ovum taken from the ovary of a woman who is not his wife—designated a “donor.” The resulting embryo is then implanted into his wife’s uterus. Recourse is had to this method when the wife’s ovaries have been removed or rendered non-functional, yet her uterus remains healthy and able to receive the embryo.

Fifth technique: external fertilization is carried out in a test tube between the sperm of a man and the ovum of a woman to whom he is not married—both labelled “donors.” The embryo is then implanted into the womb of another married woman. This procedure is chosen when the recipient wife is infertile because her ovaries no longer function, though her uterus is sound, and when her husband is likewise sterile, while both nevertheless desire a child.

Sixth technique: the gametes of a married couple are fertilized outside the body, after which the embryo is implanted into the uterus of another woman who volunteers to carry the pregnancy. This course is taken when the wife cannot sustain a pregnancy because of a defect in her uterus, even though her ovaries are healthy and productive, or when she simply prefers not to become pregnant for reasons of comfort or convenience, so another woman offers to bear the child for her.

Seventh technique: this is identical to the sixth, except that the woman who volunteers to carry the pregnancy is a second wife of the husband whose sperm is used; the co-wife offers to carry the embryo on behalf of her fellow wife. This technique does not