A new pilot program in London will make the birth control pill available next month, through pharmacists, without a prescription. It's a big shift from December 1955, when scientists made the first presentation that progesterone can stop women from ovulating, and many states had laws banning the use of contraception.
Despite nearly 50 years of access to the pill, some women are clueless about side effects that doctors might not bother sharing, and some that are just being discovered.
"Doctors in general tend to hesitate to suggest things to the patient," said Dr. Nanette Santoro, director of reproductive endocrinology at the Albert Einstein College of Medicine in New York City and a member of The Endocrine Society.
"These are things that wouldn't have a major health impact."
Santoro said, with limited time in appointments, doctors focus on the major side effects that can pose a health risk: the risk of blood clots among smokers, high blood pressure, and stroke with some migraine headaches, for example.
But Santoro knows of many less-pressing and idiosyncratic side effects from the pill that don't always make it into the doctor's talk.
Women on the pill may suffer a lackluster sex drive, mood swings, or even extra sinus pressure, she said.
"Some women may notice their sinuses are a little stuffier," Santoro explained. "It speaks to the bigger point that pills do affect the mucus production of the body."
That means mucus, whether on the cervix or in the nose, can become thicker.
This August, research began to confirm another strange connection between the birth control pill and a woman's nose.
In a study of about 100 college students in the U.K., scientists found that the pill may change how women find a man's scent sexually attractive.
The study collected body odor from volunteers and put it in jars for the ladies to smell. Among the 200-300 different chemical compounds in sweat, researchers tried to draw a connection to the woman's reaction to the sweat and a by-product in the sweat from the major histocompatibility complex (MHC) genes, which contribute to the body's immune system.
Since the late 1990s, research has shown that women find the scent of a man more attractive if he has MHC genes that are different from their own, and less attractive if he has similar MHC genes.
But that all may change two months after a woman goes on the pill.
The Pill May Change How You Choose a Man
"In the pill-using group, there was a significant shift in their preference for men who had more similar odors," said Craig Roberts, a co-author of the August MHC study appearing in the "Proceedings of the Royal Society B," and a lecturer at the University of Liverpool in the U.K.
Roberts said the women in the control group who didn't take the pill only started to find men with different MHC genes more attractive in the second round of body odor sniff tests.
"It's an odd thing to do, smell odors in jars," Roberts said. "We don't know the effects in the real world, but it does carry implications for women who are using the pill, and you can extrapolate from this very artificial laboratory study quite a long way."
For example, "They may choose someone they may not choose otherwise," he said. In theory, Roberts said a woman may choose a man while she's on the pill and feel fine, but subconsciously find her mate less attractive if she goes off the pill.
"There is evidence that couples that are more MCH similar to each other have more difficulty conceiving, and they have more miscarriages," added Roberts, who has also cited research that women who marry men with similar MCH genes are more likely to have an affair.
Aside from chemical conjectures, Einstein's Santoro has heard straight from her patients that the pill can affect one's sex life.
"Clearly, pills suppress androgen production in the ovary, so, to the extent that androgen levels drive sex drive in women, it could affect them," said Santoro, who is also a doctor with the Montefiore Medical Center in New York City.
"It's also possible for some women, especially if they're Catholics, to have a libido problem. ... Once they start on the pill, it may reduce their enjoyment in some way out of guilt," she said.
Santoro said many of her patients tend to think of the pill as an off-switch for hormones, but in truth, the pill exposes women to higher levels of hormones to overcome their own cycle.
Other Strange Side Effects From the Pill
"Because the pill in a lot of ways produces a pseudo-pregnant state, some of the side effects of pregnancy are noticed in the pill," Santoro said.
That means women on the pill may experience heartburn, or constipation, or sleep disturbances, either as insomnia or extra sleepiness.
Santoro said doctors are also less likely to get into great detail about weight changes.
"We tell our patients that weight doesn't change if you take the pill ... but among the individual women, there may be some who gain and some who lose," said Santoro, who added that large studies on the subject might cancel out the average weight changes experienced by women on the pill.
Overall, Santoro said she'd spend more time talking about the pill's more serious health risks and side effects with a patient.
"Women over 35 who smoke more than 10 cigarettes a day -- they shouldn't be taking the pill at all," she said.
For patients who have migraines with aura, which refers to feelings and symptoms noticed shortly before the headache begins, "they should not take pills without making sure everybody's on board."
Santoro said although research hasn't drawn any hard-and-fast conclusions about side effects from taking the pill for an extended period of time, many of her patients have decided to give the hormones a break.
"It's outdated, but some women feel better if they take a little 'pill holiday' now and then," she said.