Combination pill

The combination birth control pill is an oral contraceptive taken daily that contains estrogen and progestin ("the pill").

Effectiveness rate. With perfect use — if you follow the directions and never miss any pills — the effectiveness rate of the pill tops 99 percent. However, among typical users of the combined estrogen and progestin pill, the effectiveness rate is 92 percent, meaning that eight out of 100 women taking it for one year will get pregnant. Other medications can interfere with the pill's effectiveness, so talk to your doctor before taking the pill with any other drug.

Side effects and health risks. Side effects may include headaches, breast tenderness, nausea, vomiting, bloating, decreased sex drive (libido) and depression. Research has not shown any link between taking the pill and weight gain. The most serious potential complication is a slightly increased risk of heart disease, high blood pressure and blood clots. Talk to your doctor about how your health history and age may affect your risks with hormonal contraception.

Women with the following characteristics should not take combination estrogen and progestin pills:

• Age 35 or older and currently smoke
• A history of cardiovascular disease
• A history of breast, uterine or liver cancer
• A history of blood clots in the legs or lungs

The pill doesn't provide protection against sexually transmitted diseases (STDs).

How to use the pill. The pill is available in a range of hormonal concentrations. If you decide on the pill, your doctor will determine which formula best meets your needs. Take the pill according to the most recent package insert, which provides instructions on when to begin the pill, whether you need backup contraception at certain times and what to do if you miss a pill. Using the pill to decrease the number of menstrual periods you have in a year, or to eliminate regular periods completely except for occasional breakthrough spotting, has been demonstrated to be safe and is a feature of some oral contraceptive regimens.

Cost and availability. Costs vary widely, depending on which product you use, what your insurance covers and what your doctor charges for the initial visit. Pill costs range from $9 to $60 a month, and initial visits cost $35 to $175.