After new research confirms what many women knew already - that taking the contraceptive pill can help ease period problems - experts discuss the health pros and cons of the most popular form of contraception.
By Lisa Salmon.
Since its introduction to the UK 50 years ago, the tiny contraceptive pill has been subjected to enormous scrutiny and there have been many myths bandied around about it.
But new research has finally confirmed what many of the 3.5 million UK women who take the Pill already know - it eases period pain.
The 30-year Swedish study, the latest evidence in a mounting body of research into the health effects of taking the Pill, found that every third woman who took it suffered less menstrual pain, worked better and had less need for painkillers, compared with those who didn't take it.
The researchers also found women on the Pill didn't put on weight.
Here, the experts separate health fact from fiction...
:: Fact: The Pill reduces period pain At least half of all women, particularly younger ones, are thought to suffer from painful periods.
A 2009 review of research by the Cochrane Collaboration concluded there was "limited evidence" for period pain improvement from taking the Pill.
However, Dr Ingela Lindh of Gothenburg University in Sweden, who led the latest study into the effect of the Pill, questioned more than 1,000 women about their menstrual pain and contraceptive use, and found the Pill made a "significant difference".
Lynn Hearton, helpline manager at the FPA (formerly the Family Planning Association), says the findings are no surprise.
"The Pill helping with period pain is something we already knew," she says. "There's a huge range of pre-menstrual symptoms, and it's effective in reducing all of those."
While the combined oral contraceptive (COC) pill is obviously designed to prevent pregnancy by suppressing ovulation through the actions of the female hormones oestrogen and progestogen it contains, it's not licensed in the UK to treat period pain (dysmenorrhoea).
:: Myth: The Pill makes you gain weight It's a widely-held belief that the Pill makes women pile on the pounds, but the Gothenburg University study questioned women about their weight and found this wasn't the case.
Dr Lindh says: "The women who were on the Pill, and were monitored from their teenage years until the age of 34, didn't put on any more weight than their peers who had never taken the Pill at all."
The Swedish study confirms the findings of a 2006 Cochrane review of published studies on the Pill and weight, which concluded there was no substantial difference in the weight of women on the combined contraceptive pill, compared with those who took a dummy medication.
:: Myth: The Pill causes cancer An ongoing Royal College of General Practitioners (RCGPs) Oral Contraception Study of 46,000 women, which last reported in 2010, showed there was a small decrease in the mortality rates from any cause in women who'd taken the Pill, as well as a small decrease in the risk of developing cancer.
Overall, the study which began more than 40 years ago and is one of the world's largest investigations into the health effects of the Pill, showed it isn't associated with long-term health risks.
Dr Clare Gerada, chair of the RCGPs, says: "Clearly this study found there's a slight health advantage to taking the Pill, with respect to women being less likely to die from diseases such as cancer.
"My reading of it is that the Pill probably does no harm, and in all likelihood it probably gives you some protection against some conditions."
However, she stresses that women who take the Pill, especially when they're older, won't be smokers, obese, or have high blood pressure, and the RCGPs' study looked at younger women, so older women with more possible medical problems would have been excluded.
"I think you can say, at best, that the Pill doesn't appear to cause any long-term harm, and the health benefits probably outweigh any risks," she concludes.
Cancer Research UK says studies have shown that the Pill increases the risk of cervical and breast cancers, and protects against ovarian and womb cancers.
The FPA's Hearton says the risk of breast cancer increases slightly while women are on the Pill, but once they stop using it, the risk returns to normal.
"A woman might not be as concerned about breast cancer as she is about ovarian cancer, which is much more aggressive," she explains.
"Taking something that protects against pregnancy, having bad periods and that also might give some protection against ovarian cancer, may outweigh any slight risk of breast cancer."
:: Fact: The Pill prevents spots The combination of hormones in some combined oral contraceptives can work to suppress the male hormones responsible for increasing the sebum production which causes acne.
Hearton says: "The pill has a beneficial effect on acne in lots of women. Some women do take it solely for that condition."
:: Myth: You should take a break Some women feel they should take a 'Pill holiday' to give their body some time without the extra hormones.
However, Hearton and Dr Gerada both advise against this.
"If you've been on the Pill for some time, it's probably best to stay on it until you're coming off to change your contraception method, or to have a baby," says Hearton.
"If you have a break and then go back on the Pill, you restart the risks from the beginning."
And Dr Gerada adds: "There's no evidence whatsoever for a 'Pill holiday'. The worst thing is you'll get pregnant when you don't want to."
:: Fact: There's a risk of blood clots For women who aren't on the Pill, the risk of developing a thrombosis (clotting of the blood) is four to five women in every 10,000.
For those who take the Pill, the risk is nine to 10 women in every 10,000.
The additional risk disappears as soon as a woman stops taking the Pill, says Hearton.
But she warns: "You're much more likely to get a thrombosis in pregnancy than you are by taking the Pill - unless your basic risk is much higher anyway."
She says that's why it's important that anyone who wants to go on the Pill has an initial medical assessment.
The risk of thrombosis is highest in the first few months of taking the Pill, and then it levels off, says Hearton.
"If you get through those first months of using the Pill, then most of the niggly side-effects, like feeling a bit sick, and breast tenderness, all even out, as will side-effects like thrombosis," she says.
Dr Gerada points out that there is a certain group of women for whom there are risks with taking the Pill, such as those with a family history of blood clots, and smokers.
"Women who have problems on the Pill over the age of 35 tend to be smokers," she says.
"You can't quantify the risk, but it's unusual for a woman who doesn't smoke to have problems after that age."