Medicine: It's A Girl!

Picking an embryo's sex prevents the inheritance of some diseases

Many prospective parents would love to choose the sex of their child. That is now possible, according to a report last week in Nature. But the technique, developed by Dr. Alan Handyside at Hammersmith Hospital in London, is far from simple. It involves creating several test-tube embryos outside the mother's womb through in vitro fertilization. Handyside's team found a way to determine the sex of embryos that are only a few days old by analyzing their genetic material. An embryo of the desired sex can then be implanted in the womb and the other embryos discarded.

The technique is unlikely to...