Find the right birth-control method

Originally published in The Ottawa Citizen August 31, 2004

Original Title: Stop that swimmer!

What do you think are the most effective contraceptive options aside from complete abstinence (no intercourse)?

The definition of the effectiveness or pregnancy-risk of a contraception method is the percentage of women experiencing an unintended pregnancy within the first year of use.

Some are more fastidious with certain methods than others. Indeed, the method’s effectiveness depends on proper compliance or use.

Unprotected intercourse has a pregnancy rate of 850 per 1,000 women, or 85 per cent.

The choice of birth-control method can depend on cost, lifestyle, age, ease of use, previous pregnancies and children, and effectiveness of pregnancy risk.

All birth-control pills are equally effective. The reason there are so many different brands reflects the fact that each woman’s response to potential side-effects is unique. If used perfectly, three women per 1,000 will become pregnant within one year. However, many will forget to take their pill or not take it at the same time each day, resulting in a typical rate of 80 women per 1,000 or eight per cent.

Spermicides, the withdrawal method and periodic abstinence have a typical pregnancy-risk rate of 25 per cent. Condoms clock in at 15 per cent; if used perfectly the rate drops to two per cent. Female condoms fare worse at 21 per cent.

Medroxyprogesterone (depo-provera) injections must be given every 13 weeks. This has a pregnancy risk of three per cent if this schedule is not followed or the patient is taking certain medications that affect the breakdown and metabolism of the hormone. If used perfectly, the rate drops to 0.3 per cent.

The effectiveness of emergency contraception (the morning-after pill) is dependent on timing after intercourse. It is most effective within 24 hours after intercourse but can be used up to 72 hours after.

The trend for new products and procedures is to shift the pregnancy risk towards the perfect-use side. Tubal ligation (“tying the tubes”) for women reduces the pregnancy risk to five women per 1,000. Vasectomy has a risk rate of 1.5 pregnancies per 1,000. (Ladies, this is another reason to put your foot down and cite the evidence that vasectomy is the way to go.)

Two new products recently brought to market are an evolutionary change of older methods. The birth-control patch (Evra) uses the same medication found in the birth-control pill. The patch is changed once a week. It is also more forgiving. It has enough birth-control hormones to last eight to nine days. Unlike the pill, changing the patch one or two days late will not result in an increased risk of pregnancy. The patch has a pregnancy rate of three women per 1,000.

The intrauterine device (IUD) is a safe and highly effective method of birth control. Today’s IUD should not be confused with older devices such as the Dalkon shield that caused harm and was removed from the market. The IUD used today is a small T-shaped device about five centimetres long. It is a simple five- to 15-minute procedure to insert the device into the uterine cavity. Depending on the version of IUD, it provides protection from 30 months to five years.

The copper-T (Nova-T) has fine copper filament wound around the stalk of the “T.” Once inserted, it may cause some bleeding and cramping for a few days to weeks, but thereafter subsides. Six women per 1,000 can become pregnant within one year with this device.

The other version (Mirena) exchanges the copper for levonorgestrel, a variant of the female hormone progesterone. Microgram quantities of levonorgestrel released into the uterine cavity exert a local influence on the tissue. It thickens the cervical mucus to prevent the passage of sperm and blocks the sperms’ mobility and function. It has negligible extra-uterine (outside the uterus) hormonal contraceptive side-effects.

Although usually used in women who have had children, the IUD is used also in nulliparous (never-had-children) women.

The IUD is a reversible process. A small string remains on the outer edge of the cervix. Your physician uses a small forceps to grab the string and painlessly remove the IUD.

Mirena has a pregnancy-risk rate of one woman per 1,000, less than tubal ligation and vasectomy.

Consult your doctor about the potential benefits and side-effects of each option. Although many of the side-effects are minor, complete disclosure of all the potential effects is necessary.

© Dr. Barry Dworkin 2004

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