How will we have children in the future?

Pre-implantation genetic diagnosis (PGD) has been used in some fertility clinics since the 1990s, but it may become much more common in the future. Also known as embryo screening, the process involves taking a 3-day-old embryo and pulling one of its six cells to test for genetic markers of disease. Embryos that are in the clear are the ones that are implanted into a woman's womb.

Currently, PGD is most often used to test for conditions like cancer, mental retardation and blindness. It may also be used to determine which embryos are most viable for implantation in women who are prone to miscarriage, and some couples have used it in their attempts to create savior siblings, or genetic matches for a sick sibling in need of a transplant. However, some clinics have already begun using this technology to select embryos for traits like gender, a practice that is outlawed in places like the United Kingdom, India and China, but is currently legal in the United States. Some ethicists worry we're on a slippery slope to ordering up a designer baby the way we order Whoppers -- "I'd like a girl with blonde hair, blue eyes and no chance of breast cancer" doesn't sound that different from a request for a cheeseburger with onions, no mayo and extra pickles.

In a survey conducted by the New York University School of Medicine, 75 percent of respondents supported using PGD to select against mental retardation in an embryo, while 10 percent thought the process was acceptable to test for potential athletic ability. Thirteen percent of respondents could see using it to select an embryo for improved intelligence (even though environmental factors play into such a measurement), while another 10 percent would want to know about the anticipated height of an embryo before selecting it [source: Naik].

If people select for height because they don't want their kids to be short, will we lose genetic diversity and become a planet of giants? Well, not everyone wants to be tall -- there's also the issue of what's called negative enhancement, an example of which would be parents selecting for dwarfism. Some deaf parents have wanted to select deaf children, arguing that they want their child to be part of their culture. While some people may think of dwarfism or deafness as a handicap, some parents desire it, and right now, such decisions are unregulated. Who's to say what's right or wrong when it comes to a parent's wish for his or her child? Should parents be able to choose exactly what kind of child they'll raise -- and will they have the right to get rid of a child that doesn't meet specification? Expect more discussion about such issues in the coming years.

While reproductive technology has until now focused on getting more women pregnant, future technology may make it so that they don't actually have to be pregnant. There may come a day when babies grow in artificial wombs that are hooked up to a placenta machine. In 2001, Hun-Chin Liu of Cornell University began growing sheets of endometrial tissue; when the sheets proved too thin to accommodate embryos, she was able to construct a freestanding uterus. When she implanted donated human embryos, they began growing in the tissue much like they would in a woman's womb. The embryos had to be removed, though, due to regulations that limit human fetal growth in a laboratory [source: Reynolds].

In 2003, Liu implanted mouse embryos into an artificial womb; while the embryos almost reached full-term, they ended up deformed, which means this technology has a way to go before women can begin outsourcing the pregnancy process. Still, ethicists are already pondering the implications of artificial wombs. Scott Gelfand of Oklahoma State University told Nature that he could foresee a world in which women who wanted abortions would have to place fetuses in artificial wombs; the resulting children could then be adopted [source: Pearson].

Other scientists are working on growing sperm and eggs in the laboratory. In 2009, researchers at Newcastle University in England announced they had created human sperm cells from embryonic tissue [source: Park]. While the manufactured sperm resembled the real deal in looks and actions, scientists believe that sperm need a 15-year lease in some testes before they're ready to fertilize an egg [source: Park]. For now, researchers envision using the created sperm to study male infertility.

Meanwhile, scientists work on manufacturing eggs and even entire embryos. In the future, it may be possible for two gay men to have a baby together without the help of a surrogate, because eggs can be made from male cells; unfortunately, sperm requires a Y chromosome, leaving lesbian couples to rely on the help of male tissue [source: Adam]. And such a three-parent embryo isn't out of the question -- in 2008, scientists created one for the purpose of eliminating the risk of mitochondrial diseases. The scientists took DNA from the mother and the father, but removed the parts that could foretell a condition like blindness or diabetes. That DNA was implanted into a donor egg which had been scraped of all genetic information except for the tiny bit that does control production of mitochondria, ensuring the fetus ended up with all the genes he or she needed, minus the disease-causing ones [source: BBC].

Will children born without such genetic tinkering end up inferior to the ones born in the lab? For now, we're left with more questions than answers, but as we wonder at the possibilities, science keeps moving forward.