MALE INFERTILITY: Infertility affects more than 6.1 million Americans. Contrary to popular belief, it isn't usually a woman's problem. In one-third of infertile couples, the infertility is due to a female factor; another one-third of cases are linked to both male and female factors and the final one-third of cases is a sole result of male infertility. A common cause of male infertility is a varicocele -- when the veins in the scrotum are dilated on one or both sides, which affects sperm production. Other causes of male infertility include a blockage in a man's reproductive system, some medicines, low sperm count, abnormally shaped or abnormally-moving sperm, an un-descended testicle or an underlying medical problem.

AN ANSWER FOR MEN? Wolfgang Engel, M.D., Ph.D., Director of the Department of Human Genetics at the Faculty of Medicine, University of Göttingen, Germany, wants to change the future for infertile men. He's researching ways to actually grow sperm in the lab. His research has led to the first live births of mice from sperm created in the lab. His team has already produced live mice generated from sperm that was grown out of embryonic stem cells. It was a major step forward, but a sperm cell from an embryonic stem cell would still not give an infertile man a biological tie to his child. It wouldn't be any different than using donor sperm from a sperm bank, which has been done for years. To give a man a biological tie, Engel's team is now generating sperm from very early germ cells taken from the testicles. Engel says, "If it works in the mouse, I'm sure it will also work in the human." Another possibility, says Engel, is to try and generate viable sperm cells using stem cells in bone marrow. These techniques are all in very early experimental stages, but could do more than help infertile men. Engel says if sperm are able to be grown in the lab, it would be possible to take early germ cells from one woman, turn them into sperm cells, and use those to fertilize the egg of another woman. Says Engel, "It's very nice to have a woman and to have a man ... but it might be possible in the future, perhaps you are able to get a child from two women."

HOW FAR IS TOO FAR? The idea of growing sperm in the lab is raising the eyebrows of many ethicists around the world. Ken Goodman, Ph.D., a philosopher from the University of Miami, says, "The point at which you want to use a [lab-grown] sperm cell to actually make a baby -- to reproduce a human being as part of an experiment, you hit what I think is a wall. If you are creating a human being as part of the experiment, then by definition, you can't get consent from that human being. Research that uses stem-cell derived sperm for reproduction is not going to be ethically permissible." However, many people -- civilians and ethicists alike -- were offering up similar arguments when in vitro fertilization came on the scene.

Today, more than 100,000 babies have been born using IVF.