After sterilization, the birth control pill is the second most common contraceptive method used by Canadian women.

What is the birth control pill?

There are 2 kinds of birth control pills available in Canada. The combination pill uses a mixture of estrogen and synthetic progesterone or progestin. The mini-pill contains only progestin.

The first generation of combination pills came out in 1959 and contained very high doses of estrogen, which were associated with side effects such as weight gain and skin changes, and more worryingly, raised the risk of blood clots, heart attacks, and strokes, particularly in certain users. To counter these complications and to lower the rate of side effects, in the 1970s, the second generation of pills was developed with lower doses of estrogen and new types of progestin.

More recently, a third generation of pills containing even less estrogen and newer progestins has been developed with certain aims in mind: to decrease side effects such as acne and weight gain, to improve changes in cholesterol levels, and to decrease cardiovascular complications.

Even more lately, a new method for delivering contraceptives is being brought to market - the contraceptive patch. In early tests, the patch has proven to be very effective (rates of pregnancy are even lower than on the pill because women don't forget to use the patch as often as they forget to take a pill), and women have apparently really appreciated the ease of using the patch, which involves applying a patch to the lower abdomen, buttocks, upper body, or outer arm. The patch is worn continuously for 7 days, and is then replaced with another patch.

What does the birth control pill do?

In the combination pill, the estrogen and progestin combine for several contraceptive effects: inhibiting ovulation by effecting hormones such as FSH and LH, creating thick cervical mucus that slows the ability of sperm ability to fertilize an egg, making the uterus less hospitable to an implanted ovum, and other changes that prevent fertilization and implantation.

The mini-pill does not lead to as many changes and is consequently less effective than the combination pill, but when a woman can't take estrogen or doesn't want to take estrogen, the mini-pill is an acceptable alternative.

The hormones in most pills also have varying degrees of "androgen" effect, that is, they convert in varying degrees to "male hormone," which accounts for some of the side effects the pill is noted for such as acne and increased appetite.

What to do when pills are missed?

A woman who has missed only one day of taking the pill should take a pill as soon as she remembers, and probably doesn't need a backup method of birth control.

A woman who missed more than one pill should contact her pharmacist or doctor to find out the best plan to follow, and should use a backup method of birth control for at least a week.

Read "The pill: benefits" for more information.

Art Hister, MD 
in association with the MediResource Clinical Team