Blood clots are the most common serious side effect of birth control pills. Clots can occur

in many areas of the body.

pulmonary embolus.

a limb.

Any of these conditions can cause death or disability. Clots also occur rarely in the blood

vessels of the eye, resulting in blindness or impaired vision.

Women who use birth control pills have a higher incidence of blood clots. While the risk

of blood clots increases with age in both pill users and non users, the increased risk from

the pill appears to be present at all ages. The risk of clotting seems to increase with

Cigarette smoking increases the risk of serious adverse effects on

the heart and blood vessels. This risk increases with age and

becomes significant in birth control pill users over 35 years of age.

Women should not smoke.

The most significant risk factors for breast cancer are increasing age and a history of

breast cancer in the family (mother or sister). Other established risk factors include

obesity, never having children, and having your first full-term pregnancy at a late age.

Some women who use birth control pills may be at increased risk of developing breast

cancer before menopause which occurs around age 50. These women may be long-term

users of birth control pills (more than eight years) or women who start using birth control

pills at an early age. In a few women, the use of birth control pills may accelerate the

growth of an existing but undiagnosed breast cancer. Early diagnosis, however, can

reduce the effect of breast cancer on a woman's life expectancy. The potential risks

related to birth control pills seem to be small, however.

Women with the following conditions should be examined yearly by their doctors no

matter what method of contraception they use:

Oral contraceptives should not be taken by pregnant women because they may damage

the developing child. An increased risk of heart and limb and other defects has been

associated with the use of sex hormones, including oral contraceptives, during pregnancy.

In addition, the developing female child whose mother has received DES

(diethylstilbestrol), an estrogen, during pregnancy has a risk of developing cancer of the

vagina or cervix in her teens or young adulthood. Abnormalities of the urinary tract and

sex organs have been reported in male offspring so exposed. It is possible, although this

has not been demonstrated, that other estrogens such as those in oral contraceptives could

have the same effect in the child if the mother takes them during pregnancy.

There is also no conclusive evidence that the use of birth control pills immediately before

a pregnancy will adversely affect a baby's development. When a woman stops taking

birth control pills to become pregnant, however, her doctor may recommend a different

method of contraception until she has a period on her own. In this way, the pregnancy

can be more accurately dated.

Users of birth control pills have a greater risk of developing gallbladder disease requiring

surgery within the first year of use. The risk may double after four or five years of use.

The short and long-term use of birth control pills also has been linked with the growth of

benign or malignant liver tumours. Such tumours are extremely rare. Benign tumours do

not spread but they may rupture and produce internal bleeding which may cause death.

Some users of birth control pills have unpleasant side effects. These side effects are

temporary and are not hazardous to health.

There may be tenderness of the breasts, nausea, and vomiting. Some users will

experience weight gain or loss. Many of these side effects occurred with high dose

combination birth control pills. These side effects are less common with the low dose

pills prescribed today.

Unexpected vaginal bleeding or spotting and changes in the usual menstrual period also

an indication to stop taking birth control pills.

Unless more significant complications occur, a decision to stop using the pill or to change

the brand of pill should be made only after three consecutive months of use.

Occasionally, users develop high blood pressure that may require stopping the use of birth

control pills. High blood pressure may persist after stopping the pill and may lead to

serious disease of the kidney and circulatory system.

Other side effects may include:

Infrequently, there is a need to change contact lens prescription or an inability to use

contact lenses.

A woman's menstrual period may be delayed after stopping birth control pills. There is

no evidence that the use of the pill leads to a decrease in fertility. As mentioned, it is

wise to delay starting a pregnancy for one menstrual period after stopping birth control

pills.