TUESDAY, May 15 (HealthScout) -- For a tiny percentage of parents, the big question after birth -- boy or girl? -- is impossible to answer. Due to a quirk of nature, their babies appear to be both male and female.
A new study suggests that some of these babies may have a genetic defect that makes them male on the inside -- in their chromosomes -- and female on the outside.
What to do for these babies remains as controversial as ever, though.
The new research "doesn't give us the answer of what will happen later to these babies, but it's helpful to tell the parents what's going on," says Dr. Eric Vilain, study co-author and assistant professor at the University of California at Los Angeles.
An estimated 1 percent of babies are born with malformed genitals, usually minor problems that can be fixed surgically, like undescended testicles or malformed openings of the urethra.
But about one of every 3,000 babies has a more serious problem -- severely malformed or so-called "ambiguous" genitalia. The gender of the child may not be obvious, some internal sex organs may be missing, or the sex organs may have both male and female characteristics.
Surgery often is recommended, but an operation may lead to psychological problems and sexual dysfunction later in life.
Complicating matters is the lack of knowledge about why these babies are born this way.
"We are just starting to unravel this," says Dr. Melvin Grumbach, a pediatrician and professor emeritus at the University of California at San Francisco.
Vilain's study looked at what happens genetically when the sexual organs of mice begin to form in the womb. His findings are reported in the May issue of the American Journal of Human Genetics.
Vilain discovered that sexual problems arise in males when a gene known as WNT-4 appears twice on chromosomes instead of once.
The so-called "double dose" of the gene overwhelms the body's natural inclination to form testicles in a male, says Grumbach. "It's a very powerful element," he says.
Although babies with the double gene don't have testicles and appear to be female, they lack internal female organs like ovaries and a uterus.
Vilain acknowledges that his research may not help parents and doctors decide what to do about sexually ambiguous babies.
He says the problem is an "unspoken topic," and parents have few places to turn and little, if any, knowledge about the problem.
"They have this feeling of shame. They don't want to talk about it to anybody in their family or their friends. They don't want people to know, and that complicates the medical decisions about it," Vilain says.
Many parents want to make a quick decision for surgery, "so that their baby looks like everyone else," Vilain says. "Lots of parents cannot stand the idea of not doing anything."
But it's far from clear if surgery will "result in adults who will be happy, with a happy sex life," he says.
What To Do
To learn more about sexually ambiguous babies and prospects for treatment, visit this guide developed by the Johns Hopkins Children's Center.
If you'd like to reach an expert on this subject, visit this list of members of the
North American Task Force on Intersexuality.
You also might want to read previous HealthScout articles on sexuality.
