Why do so many women have difficulty reaching orgasm? A new study suggests that, for some, an anatomical disorder may be to blame. Researchers at Boston University School of Medicine report that roughly one quarter of the women they have treated for sexual dysfunction have clitoral phimosis, which means the hood of skin surrounding their clitoris is too tight or there is no opening in the skin for the glans of the clitoris to protrude for stimulation. The scientists, who were led by Irwin Goldstein, presented their findings at the Female Sexual Function Forum, a four-day meeting in Boston of physicians and therapists that ended Sunday.

The analysis was based on photographs taken of the vulvas of roughly 200 women who have been evaluated at Boston University's Woman's Sexual Health Clinic since its opening in 1998. The photos were made during examinations in which a physician placed a finger on either side of each woman's clitoris to retract the clitoral hood. Goldstein and his co-workers found that women with the highest degrees of phimosis were the most likely to report problems experiencing orgasm. Clitoral phimosis is roughly equivalent to an uncircumcised man with an extremely tight foreskin. Such men often cannot achieve an erection because it is painful; the condition is easily remedied by circumcision or surgical loosening of the foreskin. There is no standard treatment for clitoral phimosis, although some women have undergone surgery to increase the exposure of the clitoral glans.

Goldstein speculates that many women with clitoral phimosis are never diagnosed because gynecologists generally avoid the clitoris during routine pelvic examinations. He says more research will be needed to determine the overall incidence of clitoral phimosis and the degree to which it underlies female sexual dysfunction. More than 40 percent of women (and 30 percent of men) in the U.S. experience some form of sexual problem, according to a study published last year in the Journal of the American Medical Association.