If you're considering taking birth control pills, you're not alone. Birth control pills are some of the most popular contraceptives. And for good reasons — they're effective and easy to use. The variety of birth control pills available, though, can seem daunting. Fortunately, they can be sorted into just a few categories to make it easier to understand your options.

There are two main kinds of birth control pills:

• Combination birth control pills. This type of pill contains both estrogen and progestin. There are a wide variety of combination pills to choose from, depending on how often you want to have periods and the dose of hormones that is best for you.
• The minipill. This type of pill contains only progestin. The minipill doesn't offer as many choices as combination pills. In each pack of pills, all the pills contain the same amount of progestin and all the pills are active. The progestin dose in a minipill is lower than the progestin dose in any combination pill.

Combination birth control pills come in different mixtures of active and inactive pills, depending on how often you want to have periods:

• Conventional. Conventional packs usually contain 21 active pills and seven inactive pills, or 24 active pills and four inactive pills. Bleeding occurs every month when you take the inactive pills.
• Continuous dosing or extended cycle. These packs typically contain 84 active pills and seven inactive pills. Bleeding generally occurs only four times a year, during the time when you take the inactive pills. Formulations that contain only active pills — eliminating bleeding — also are available.

Combination birth control pills are also categorized according to whether the dose of hormones in the active pills stays the same or varies:

• Monophasic. In this type of combination birth control pill, each active pill contains the same amounts of estrogen and progestin.
• Multiphasic. In this type of combination birth control pill, the amounts of hormones in active pills vary.

Most combination birth control pills contain 10 to 35 micrograms of ethinyl estradiol, a kind of estrogen. Women who are sensitive to hormones may benefit from taking a pill that contains a dose of estrogen at the lower end of this range. However, low-dose pills may result in more breakthrough bleeding — bleeding or spotting between periods — than higher dose pills.

Combination birth control pills prevent your ovaries from releasing an egg. They also slow an egg's progress through the fallopian tubes, thicken cervical mucus and thin the lining of the uterus (endometrium). All of these actions help keep sperm from joining the egg.

The minipill slows an egg's progress through the fallopian tubes, thickens cervical mucus and thins the endometrium — all of which help prevent sperm from reaching the egg. The minipill sometimes also suppresses ovulation.

No. Your doctor will ask about your medical history and any medications you take to determine which birth control pill is right for you.

Your doctor may discourage use of combination birth control pills if you:

• Have just given birth
• Are older than age 35 and smoke
• Have poorly controlled high blood pressure
• Have a blood clotting disorder or a history of deep vein thrombosis or pulmonary embolism
• Have a history of breast cancer
• Have a history of stroke or heart disease
• Have diabetes-related complications
• Have liver or gallbladder disease
• Have a history of migraines with aura
• Have unexplained uterine bleeding
• Will be immobilized for a prolonged period due to major surgery
• Take St. John's wort, or anticonvulsant or anti-tuberculous agents

Your doctor may discourage use of the minipill if you:

• Have breast cancer
• Have certain liver diseases
• Have unexplained uterine bleeding
• Take anticonvulsant or anti-tuberculous agents

Pros

• Easily reversed method of birth control if you hope to get pregnant
• Relief from premenstrual syndrome (PMS)
• Less severe menstrual cramps (dysmenorrhea)
• Improvement in acne
• Shorter, lighter and more predictable periods, or fewer or no periods
• Reduction in heavy bleeding (menorrhagia) and related anemia
• Reduced symptoms of endometriosis
• Lowered risk of ovarian, endometrial and colorectal cancers
• Possible positive effect on bone mineral density
• Improvement in unwanted hair growth (hirsutism) caused by polycystic ovary syndrome

Cons

• Skipping pills or taking them late may reduce effectiveness
• No protection against sexually transmitted infections, including HIV
• Increased risk of high cholesterol, heart attack and stroke
• Increased risk of blood clots, especially for smokers and women older than 35 years of age, with a slightly greater risk of blood clots linked to pills that contain higher doses of estrogen
• Increased risk of cervical cancer and breast cancer for women who are currently taking combined birth control pills, but this risk appears to gradually decline to normal levels once you stop taking the pills
• Side effects such as irregular bleeding, bloating, breast tenderness, nausea, depression, weight gain and headache

Pros

• Easily reversed method of birth control if you hope to get pregnant
• Can be taken even if you have certain health problems that increase the risks of taking combined pills, such as blood clots, migraines, high blood pressure or a high risk of heart disease
• Are less likely than combined pills to interfere with breast-feeding
• Lowered risk of endometrial cancer

Cons

• Must be taken at the same time every day — if you skip a pill or take a pill more than 3 hours late, you need to use a backup form of birth control for at least two days
• No protection against sexually transmitted infections, including HIV
• Side effects such as irregular menstrual bleeding, ovarian cysts, decreased libido, headache, breast tenderness, acne, weight gain, depression and hirsutism
• Slightly increased risk that if pregnancy occurs, the fertilized egg will implant outside the uterus (ectopic pregnancy)

You have many options for birth control. If you choose to take birth control pills, work with your doctor or other care provider to decide which type of birth control pill is right for you.