Jose and Claudia Quintero of Miami, Fla., already had three daughters and wanted a boy to round out their family. Lisa Kreshock of Leonard, Mich., had a strong yearning to add a daughter to her and her husband's family of two boys when she lost her mother to Alzheimer's disease.
Thanks to modern technology, both couples got what they wanted.
Since Dolly, the cloned sheep, was born in 1997 and jolted the world with the controversial possibilities of genetic manipulation, scientists have been talking about moral dilemmas we may face in the future, from human cloning to designer children.
Some say the ability to select the gender of unborn children marks the start of that future. And while the science is here, society seems everything but settled on the implications.
"Children are the issue of our love, not the product of our wills," the members of the President's Council on Bioethics said about gender selection in a recent report.
The United Kingdom has already clamped down on the practice of pre-selecting the gender of embryos for non-medical reasons. Authorities there ruled that only families with a history of gender-linked genetic disorders could tap the technology.
"Great value should be put on the unconditional nature of parental love," Suzi Leather, head of the U.K.'s Human Fertilization & Embryology Authority,said at the time of the November 2003 ruling.
But others argue, what's the harm in choosing?
"When a couple has a strong preference for a baby boy or girl, who is injured by allowing them to choose? Certainly not the child," says Gregory Stock, director of medicine, technology and society at the University of California's School of Public Health in Los Angeles.
Sorting Sperm, Not Embryos
That argument has taken on more force now that some methods have become available which don't require the ethically thorny practice of creating and then discarding embryos of the unwanted gender.
The newer techniques sort sperm, rather than embryos.
Read about methods people may try to select the gender of their child here.
Every cell in the human body contains 46 packages of DNA known as chromosomes, which are divided into 23 pairs. One of these pairs contains sex chromosomes. Women have two X chromosomes while men have one X chromosome and one Y chromosome. The factor that determines a child's sex is which of the man's sperm reaches the female egg.
About half of a man's sperm contain girl-producing X chromosomes, while the other half contain boy-producing Y chromosomes — whichever kind of sperm reaches the egg first wins. But the new methods, some of which remain in question within the medical community, try and control that coin toss.
The Microsort method, available since 1995, is the most widely accepted of these methods. It's based on the fact that X chromosomes are bigger than Y's, so when the sperm cells are doused in a special fluorescent dye, the X chromosomes soak up more of the dye and glow brighter.
The sperm is sorted this way, and then assigned a charge, which tugs them into separate receptacles. The couple selects the boy or girl-producing sperm and uses it for fertilization. The technique (used by the Quintero family) costs about $5,000 per try and is 88 percent effective for couples desiring girls and 73 percent effective for those wanting boys.
Other, slightly older techniques also rely on the weight differences between X and Y chromosomes to sort them, but remain less proven.