Since Louise Brown, the first baby conceived outside a human body, was born in England in 1978, techniques for helping infertile couples conceive have mushroomed. It is now possible to have a baby with, say, five parents—the provider of donor egg, the provider of donor sperm, the surrogate mother who undergoes pregnancy, and the two contractual parents. Two of the following methods remain experimental.
Fertility drugs: These drugs stimulate the ripening and release of eggs from the ovary, making conception through intercourse more likely.
Intrauterine insemination: Sperm, either from a partner or a donor, is injected through a catheter into the uterus during ovulation, the period when an egg is released into the fallopian tube.
In vitro fertilization (ivf): Eggs are extracted from the ovaries and mixed with sperm in a petri dish. Once fertilization has occurred, the eggs are incubated for 2 to 3 days. Then the healthiest embryos are inserted into the woman’s uterus. She will have been taking hormone supplements to build up the uterine lining for accepting embryo implantation.
Gamete intrafallopian transfer (gift): Sperm and eggs are inserted into the fallopian tube in a surgical procedure. Because gametes normally meet in the fallopian tube, gift is thought to boost slightly the chances of successful fertilization.
Zygote intrafallopian transfer (zift): Much the same as gift, except that the egg is fertilized outside the body, then inserted into the fallopian tube as a zygote—an egg that has been fertilized but has not yet begun cell division.
Assisted hatching (ah): The outer membrane, or shell, of the embryo is punctured to aid implantation in the uterus.
Intracytoplasmic sperm injection (icsi): A single sperm is injected into an incubating egg cell. Useful in cases where ordinary ivf has failed.
Egg donation: An egg from a donor is fertilized and then implanted into another woman’s uterus. This technique can be used for women whose own ovaries are not functioning due to disease or aging—an older woman’s uterus has no problem accepting an embryo even when the woman is well past menopause.
Surrogacy: A woman who contracts to undergo a pregnancy for another woman. The baby is conceived with the surrogate’s egg and the contractual father’s sperm. Alternatively, a couple can transfer an embryo conceived with their own gametes into a surrogate mother’s uterus. By this method, a woman for whom pregnancy is impossible or health-threatening can have a biological child.
Embryo donation: A couple receives a surplus embryo from another couple’s ivf efforts.
Cytoplasmic transfer: The cytoplasm—the material in a cell that surrounds the nucleus—is extracted from a younger woman’s egg and inserted into an older woman’s egg. Cytoplasm from a young egg may reduce errors in the genetic material of the older woman’s egg, enhancing the chance of successful fertilization.
Egg freezing: One of the most recent—and still experimental—developments, in which eggs are extracted and frozen for years, just as sperm are. Young women could freeze their eggs, then use them at age 35 or more to reduce the risk of creating fetuses with chromosomal abnormalities. Whether most eggs can survive freezing without damage to their dna is not certain.
Nuclear transfer: This procedure is currently used only in research. The nucleus from an older woman’s egg is slipped into a donor egg that has had its nucleus removed. Providing an electrical spark simulates fertilization, and the egg begins the cell division that will allow it to become an embryo. Someday this transfer procedure might facilitate pregnancy in an older woman: after the nucleus from her egg is slipped into a young woman’s egg, the egg would be fertilized in normal in vitro fashion and transferred into the older woman’s uterus. Creating an offspring from two same-sex parents might also be possible, at least in theory. It is easiest to imagine how this could happen with two men. The nucleus from a body cell from one partner could be slipped into an enucleated donor egg. The other partner’s sperm might be able to fertilize that egg, which could then be implanted in a surrogate mother. Whether an egg fertilized in this fashion would survive is not known.
