Is it a boy or a girl? It's the first question most parents ask about their newborn baby. But for a surprising number of infants, the answer is not immediately obvious.
Doctors say as many as 1 in 2,000 babies is born with ambiguous genitalia — neither totally male nor female. For parents, the decision about how to proceed is often agonizing, and the stakes are high: the wrong choice could trap a little boy inside a girl's body or create a girl who longs to be a man.
Now a new study in the New England Journal of Medicine is shedding more light on what factors make us feel male or female. The research examined 16 genetically and hormonally male babies born with a rare birth defect called cloacal exstrophy (unlike cases where the genitalia are ambiguous, male babies born with cloacal exstrophy have a small or non-existent penis).
Traditionally, doctors believed that without a penis, these children would not be able to form a healthy male sexual identity. So, 14 of the 16 babies were assigned the female sex, given female hormone treatments and raised as girls.
But follow-up questionnaires given years later suggest that the female label did not stick very well.
"These children were born male in nearly every respect," explains study author Dr. John Gearhart, professor and chair of pediatric urology at Johns Hopkins Hospital in Baltimore.
The Key? Hormones
Gearhart found eight of the 14 subjects now declared themselves male. All 16 of the children enjoyed typical "male" pursuits such as baseball, football, and hockey. Only one played with dolls, and most rejected feminine clothing.
The study illustrates what was once unthinkable — that a person can feel like a male without a penis — is completely possible, maybe even predictable, given what we now know about how sexual identity is formed.
Hormones are key. "What we now know is that hormones imprint your brain," explains Dr. Craig Peters, a urological surgeon at Children's Hospital in Boston. "We don't know exactly when it happens, but probably even in utero."
Studies like Gearhart's have helped change policy. Now male babies born with cloacal exstrophy would be recognized as male. "One very seldom does gender conversion [for this condition] anymore," Gearhart says.
Yet surgery for other conditions, especially those involving ambiguous genitalia, is still common. "Probably the most common condition for gender conversion is male pseduo-hermaphroditism," Gearhart explains.
So How Do Parents Decide?
Parents and doctors have a variety of scientific tools to tell aid them in determining a baby's sex if the genitalia are ambiguous. Genetic testing is performed to check for the presence of a "Y" chromosome. Males are XY; females are XX.
An internal exam determines the shape of the pelvis and checks for the presence of female sex organs like ovaries and a uterus. Physicians evaluate whether the person has the potential to be a fertile male or fertile female.
Doctors also check the baby's levels of male hormones (called androgens, like testosterone) and female hormones (such as estrogen). In each case, the sex hormones are created by the gonads — testes for males and ovaries for females.
But production of hormones is only half the battle. The body must have receptors that sense the presence of the hormones or sexual characteristics will not develop normally.