In one out of every 3,000 births, the physician cannot tell the new parents what some have waited to hearnamely, whether they have had a boy or a girl. But the results of a study described in the May issue of the American Journal of Human Genetics may offer new hope to parents whose infants are born sexually ambiguous. According to the report, researchers have determined that a second copy of a sex determination gene known as WNT-4 can change an embryo from male to female, which often results in ambiguous genitalia. The finding could help doctors more accurately and quickly identify an externally ambiguous babys gender.

Geneticist Eric Vilain of the University of California at Los Angeles and his colleagues identified WNT-4 as one of several genes that determine sex. Whereas most genetic defects stem from the absence or mutation of a gene, genital defects arise when WNT-4 appears twice on the chromosome. WNT-4, it seems, "influences the sex determination pathway at each step of the way," Vilain notes. "We discovered that when the amount of the gene fluctuates even slightly at any stage in the genetic blueprint, it changes the embryo from male to female."

The WNT-4 study results will enable researchers to use genetic testing to help identify the causes of genital ambiguity. Moreover, scientists might one day even be able to treat a defective embryo in utero. "Our findings suggest that clinicians could identify the WNT-4 duplication prenatally," Vilain remarks. "If this proves true, in the future we may be able to correct the defect in the womb and restore the embryo to its original male status. This may repair the genital malformations before the child is born."