"It'll be upsetting because some women will think, 'Oh my God, maybe I just can't.' On the other hand it takes away a kind of guilt or pressure," said Dr. Virginia Sadock, director of the human sexuality program at New York University Medical Center.

Either way, specialists say the findings don't mean women who inherit an unfortunate gene package are doomed. They just mean that more work, or patience, is required.

Better Treatments for Sexual Problems

The main benefit of discovering the genetic elements of sexual function, experts say, is to help scientists find better treatments for sexual problems. The study was reported this week in Biology Letters, a journal of the Royal Society, Britain's independent academy of science.

In the study, scientists from St. Thomas' Hospital in London sent questionnaires to 4,037 women who are part of the British twin registry. About half of them were identical twins and half were non-identical twins.

One in three of the women reported never or hardly ever reaching orgasm during intercourse and 21 percent said they hardly, if ever, achieve climax during masturbation. Those figures are consistent with other surveys conducted over the last few decades.

However, the questionnaires revealed a significant genetic influence on the ability to reach orgasm, said lead researcher Tim Spector, a genetic epidemiologist at St. Thomas' Hospital.

The similarity in orgasm experience was greater in identical twins than it was in non-identical twins, Spector said. Because the only difference between the two groups was genetic, the researchers concluded that the gap between the groups was the genetic component.

Can't Rule Out the Genetic Argument

After taking into account other factors that could influence orgasm, the scientists estimated that 34 percent of the difficulty women face in reaching orgasm during intercourse is due to genes.

Problems in sexual response during masturbation seemed to be more genetically influenced than orgasm ability during intercourse. The study found that 45 percent of the difficulty women have in climaxing during masturbation can be attributed to genetic makeup.

The results were similar to those of a study on Australian twins published earlier this year.

The idea that orgasm ability has a genetic component makes sense, said female orgasm expert Laura Berman, a professor at the Feinberg School of Medicine at Northwestern University in Evanston, Ill.

"A lot of the women that I treat will tell me that when they talk to their siblings or mothers they very often have similar challenges," said Berman, who was not involved with the study. "One could make the case that it's nurture, not nature, because these twins were brought up together, but you can't rule out the genetic argument."

But Spector said effects of the twins' shared environmental influences did not alter the study results significantly.

Women Are More Complex Sexually

Even if women do inherit an unfavorable genetic mix, as with many other conditions, it does not mean they are doomed, experts said. Many approaches can help most women enhance their ability to achieve orgasm.

"Factors influencing the ability to (reach) orgasm vary from woman to woman. What we do know is that psychologically women are more complex sexually," Sadock said. "For women, being in a relationship where they feel loved and feel secure is a big factor. Other big factors are how they feel about themselves and about sex and what their first experiences were."

"Maybe there are some women ... who can never. That is a possibility, but that would be a small amount," Sadock said.

And even if they can't, that doesn't mean there's no joy for them in sex, Berman added. A survey she recently conducted found that among women enjoying satisfying sex lives, orgasm did not rate as a key element for fulfillment.