How the Birth Control Pill Works

Birth Control Pill Side Effects

In addition to preventing pregnancy, the pill can have all sorts of side effects -- some negative, some positive. The most common side effect of the pill is breakthrough bleeding or spotting, which is when a woman bleeds in the weeks she's taking active pills. This is due to the changes in hormone levels. Most women's bodies adjust after a few months of being on the pill.

Other common side effects include:

  • nausea
  • headaches
  • breast soreness
  • acne
  • decreased libido
  • depression
  • moodiness
  • weight gain

Many of these symptoms are due to the estrogen in the pill. Sometimes they go away after a few cycles, but if they don't, a woman might need to switch to a different formulation.

The pill also carries some more serious, although rare, risks. Taking the pill increases a woman's risk of high blood pressure, blood clots, strokes, heart attacks, liver tumors and gallstones. Some of these conditions can be fatal, but the risk of experiencing any of them is very low.

A woman is more at risk if she's overweight, older than 35 years old, smokes, has diabetes or already has high blood pressure or high cholesterol. Some studies have linked taking the pill to an increased risk of breast and cervical cancer, while others show no increased risk. The most recent theory is that the increased risk is temporary and only occurs within the first five years of taking the pill, when the risk of contracting these types of cancer is already very low. Women who stop taking the pill eventually go back to having the same risk factors for these cancers as before.

But the pill can also reduce cancer risk: A January 2008 study in the medical journal The Lancet showed that the longer a woman took the pill, the lower her risk of ovarian cancer.

For many healthy women without risk factors, the benefits of taking the pill tend to outweigh the risks. Women on the pill often report shorter, lighter menstruation, fewer and less painful cramps and better skin. The pill can fix irregular periods, reduce iron deficiencies (as less blood is shed during menstruation) and reduce the risk of benign cysts in the breasts or ovaries.

Women with polycystic ovarian syndrome (PCOS) and premenstrual dysphoric disorder (PMDD), an extreme form of PMS, can also find relief from some of their symptoms by taking the pill

We've been talking about "the pill," but the truth is, there are many pills. Next, we'll look at the differences between them.