Low Dose Birth Control Pill

What's in a Birth Control Pill

Most birth control pills contain two hormones, estrogen and progestin. Both are similar to hormones that are made naturally in a woman's body. At the doses contained in a birth control pill, the hormones act to disrupt a woman's normal menstrual cycle. Instead of releasing an egg once a month, the ovaries behave as if the woman is already pregnant. For most women, ovulation stops.

Many women take birth control pills for years without any problems. However, the hormones can cause side effects. Sometimes reducing the dose of estrogen can help.

Definition of "Low-Dose"

The original birth control pill, introduced in 1960, had a high dose of estrogen. At that time, doctors didn't know that a lower dose would be effective. Side effects of the high estrogen dose included increased risk of heart attack, stroke, and dangerous blood clots. Doctors soon figured out that these risks were related to the amount of estrogen. Around the same time, studies also showed that a lower dose would still prevent pregnancy.

Early versions of the low dose birth control pill contained 50mcg of estrogen, compared to the original 100 to 175mcg dose. Today, many pills contain only 30 to 35mcg, and "very low dose" pills have as little as 20mcg of estrogen.

Advantages and Disadvantages

Low dose pills carry a lower risk of heart attack, stroke, and blood clots than their predecessors. For some women, taking a low dose birth control pill may also help with other, more minor side effects.

Side effects that may improve with a lower estrogen dose include:

• Weight gain
• Nausea
• Breast tenderness

Some people think that a low-dose pill can reduce the risk of depression or mood swings, but it's the progestin in the pills that seems to cause emotional side effects. Progestin is necessary to prevent pregnancy, but changing brands of pills may help.

Women who use low dose birth control pills sometimes experience bleeding or spotting between periods. A higher dose of estrogen may be necessary to keep this from happening.

Who Should Not Take Birth Control Pills?

Even with the lower estrogen dose, some women should not take birth control pills. For example:

• Women who smoke appear to be at higher risk of heart attack and stroke.
• Women who have had blood clots in the past should not use the pill.
• Women with a history of heart attack or stroke are generally advised to avoid birth control pills.
• Women with a history of breast cancer should not take hormonal contraceptives, including the pill.

And, some women who can use them will need to be monitored carefully by a doctor.

Effectiveness of the Low Dose Birth Control Pill

The low dose birth control pill is very effective. Just like higher dose pills, low dose pills are considered greater than 99% effective if used correctly. That means that, if a woman takes the pill regularly and follows the directions precisely, she has less than a one in 100 chance of becoming pregnant each year. With typical use, allowing for the occasional mistake, effectiveness is probably only about 95%.

Very Low Dose Birth Control Pills and Menopause

Women who are approaching menopause sometimes think that they can't get pregnant. Their periods become irregular or get farther apart. And, to many women, it just seems incredible that a pregnancy could happen at that age.

However, women who are near menopause can indeed still get pregnant. At the same time, the risk of serious side effects from the estrogen in birth control pills appears to be higher in older women. Very low dose birth control pills are an option for preventing pregnancy while minimizing side effects.

Very low dose pills aren't the best choice for everyone. Some older women already have a history of heart attack, stroke, or other serious problems that could make taking the pill dangerous. Some women will find that the pill makes their periods more irregular. However, many women find that very low dose birth control pills are a convenient and effective choice.