A Girl or Boy, You Pick

She had the name picked out since high school: Logann Rae, taken from a soap opera. She had two dolls waiting in a closet, both saved since childhood. Tanya had always dreamed of having a daughter, and of the intimate bond that would grow as they picked out dresses together, styled their hair and painted their fingernails. But Tanya's first child was a son. Then came another. When an ultrasound showed that her third child was also a boy, she struggled to hide her tears from the nurse.

And that is why this year she drove 400 miles to a doctor's office in Westwood. Using methods common in fertility clinics, doctors mixed Tanya's eggs with her husband's sperm to create five embryos in a laboratory dish. Then, using a new technique, they examined the embryos to determine which had the DNA to become boys, and which were programmed to be girls.

The three male embryos were frozen, their fate to be decided later. The two female embryos were transferred to Tanya's womb in an attempt to create the daughter she...