Moving beyond Mother Nature: The Anatomy and Physiology of Reproduction - dummies

Moving beyond Mother Nature: The Anatomy and Physiology of Reproduction

By Janet Rae-Dupree, Pat DuPree

Assisted reproduction goes above and beyond people’s usual ideas about how humans make babies. Here is a glimpse into what humans have been doing to help Mother Nature perpetuate the species.

  • Fertility medication: Used to treat female infertility, these drugs are used primarily to stimulate ovulation. The most widely used drug, clomiphene (known in the U.S. by the brand name Clomid), inhibits estrogen receptors in the hypothalamus, which results in the pituitary releasing more of the hormones required for ovulation. Doctors also sometimes prescribe drugs to stimulate the hypothalamus to release hormones called gonadotropins, or they introduce gonadotropins directly, either from natural sources or created artificially. Some studies indicate that Clomid taken in combination with Vitamin E can partially reverse oligospermia, or male infertility.

  • Intrauterine insemination (IUI): More popularly known as artificial insemination, this procedure uses a long, narrow tube to place sperm directly into the uterus. It’s used for myriad reasons, including when women have scarring or defects of the cervix, or when low sperm count or motility makes natural insemination unlikely to lead to pregnancy.

  • In vitro fertilization (IVF): This means simply that fertilization occurs outside of the body. Known as the most effective assisted reproductive technology, or ART, this procedure long has borne the misnomer of “test tube babies.” Rather than a test tube, fertilization takes place in a flat Petri dish. IVF begins with fertility drugs to stimulate the ovaries to produce multiple eggs. When the eggs mature, they are “harvested” from the ovaries and mixed with sperm. After three to five days, one or more of the resulting blastocysts are transferred into the uterus.

  • Zygote intrafallopian transfer (ZIFT): Also known as tubal embryo transfer, this procedure is similar to IVF, but the zygote is transferred earlier and into the Fallopian tube instead of the uterus.

  • Gamete intrafallopian transfer (GIFT): Eggs and sperm are collected artificially, as in IVF, but in this case the harvested eggs and sperm are placed together into the Fallopian tube instead of a Petri dish, so that fertilization takes place inside the body.

  • Intracytoplasmic sperm injection (ICSI): The usual steps of IVF are followed, and the eggs are harvested, but rather than being mixed in a Petri dish, a single sperm is injected into each mature egg before the blastocysts are transferred either into the uterus or the Fallopian tube. This option can be used when there is a very low sperm count, when there are problems with motility, or if the sperm must be collected directly from the testicles or epididymis.

In addition to technical interventions, assisted reproduction also can involve the use of eggs donated from another woman, donated sperm, or frozen embryos created during a couple’s earlier IVF cycles or donated from an unrelated couple. These options sometimes are chosen if a couple carries a genetic disease that could be passed on to a baby, if a woman has older eggs, or if she cannot ovulate.