Testosterone is behind the sexual drive in both males and females.

As females have much lower testosterone levels, their sexual drive is lower, but will it become even lower if we add the female sex hormones from the contraceptive pills?

A meta-analysis of 25 years of studies made by Dr. Jonathan Schaffir, an obstetrician and gynecologist with the medical center, revealed that the pill has little - if any - impact on a woman's sex drive. The early pills, developed in the 1960s, often contained high levels of estrogens and progestins (female sex hormones), up to 150 mg in single doses.

This cocktail made women become bloated, feel breast tenderness or experience nausea. "These side effects could easily have caused women to feel extremely uncomfortable, translating into decreased libido," said Schaffir. "Also much less was known about the human sexual response at that time, which could have led to information based on opinion and not on fact."

Schaffir looked if certain types of hormonal contraception or some individuals are more vulnerable to libido changes. Some women, indeed, seem to be prone to libido decrease while taking oral contraceptives. "When looking for a consistent biological effect of hormonal contraception on sexual desire, androgens would probably be the factor most suspected to play a role", said Schaffir. "It was shown that the birth control pill decreased the concentration of free androgens, including testosterone, but that doesn't necessarily translate to a loss of libido. Chemical changes occurred, but they did not apparently impact sexual behavior for the vast majority of women," he said.

Progestin's effect on libido seems also to be weak. "A small minority of all the users of progestin were actually bothered by a low libido," said Schaffir.

After 1975, only a small percentage of pill users suffered a decrease in sexual desire. "Studies showed that it was a problem for a small number of women using birth control pills to experience decreased libido, but it didn't happen predictably in any specific sub-population, or with any particular type of hormonal contraception," said Schaffir. "In fact, changes in sexual desire could as likely represent a combination of biological, psychological and social phenomena as any hormonal effect."

"The available literature illustrated that decreased libido is an idiosyncratic, unpredictable reaction in a small minority of women."

"Don't let such fear factor into your decision of whether to take hormonal birth control pills," added Schaffir.