Womens Health

Bleeding Expectations on Oral Contraceptives

Frederick R. Jelovsek MD

Oral contraceptives have many benefits for control of bleeding during the menstrual cycle. They also have side effects and complications that make their use unsatisfactory. Almost a third of women who discontinue birth control pills do so because of bleeding problems. Then what kind of bleeding can you expect when using birth control pills? A recent supplement to the American Journal of Obstetrics and Gynecology, 1999;180:s275-306 had several articles about oral contraceptives and bleeding.

Does birth control pill use lessen abnormal menstrual bleeding?

Oral contraceptives reduce the overall incidence of bleeding problems by about 50% from what occurs in non-contraceptive users. The rate of heavy menses in the general population is about 2.4%. In women on birth control pills it drops to 1.2%. Irregular menses goes from 1.3% normally to 0.5% in oral contraceptive users. Intermenstrual bleeding (breakthrough bleeding as a recurrent problem) decreases from 0.5% to 0.3% in women who have been on oral contraceptives over time.

How much breakthrough bleeding can I expect when starting oral contraceptives?

Studies have shown differences in breakthrough bleeding rates in the first 3 months of women starting birth control pills ranging from 10%-55%. Even the same pill in different studies has widely varying rates. The rates are so high that routine advice upon starting the pills is to ignore the breakthrough bleeding for the first 3 months of use; then if it persists let the doctor know.

Does the bleeding get better the longer I take the pills?

Yes. The intermenstrual bleeding rate drops to about 10-15% in the 4th and subsequent cycles and in most studies does not seem to lessen after that. This is still a high percentage of bleeding so it causes many women to discontinue the pills.

What causes bleeding while on the birth control pills?

The most common cause of bleeding on oral contraceptives is unknown. It is theorized to be due to atrophic bleeding due to low estrogen. In other words, the lining of the uterus (endometrium) is quite thin and subject to abrasion just from normal activity.

There are three other factors known to be associated with increasing the bleeding rate on pills: chlamydia infection, smoking and not taking pills. In one study, women with intermenstrual bleeding on birth control pills had a 29% incidence of chlamydia while oral contraceptive users without intermenstrual bleeding had a 11% incidence of infection versus 6% in non-pill users. Several studies have confirmed an increase in intermenstrual bleeding associated with chlamydial infection on pills.

Cigarette smoking has been known to be associated with anti-estrogen effects. While new users have less and less intermenstrual bleeding with each cycle of pill use, non-smokers decrease breakthrough bleeding at a much faster rate than smokers. By the 6th month of pill use, smokers still have about twice the rate of spotting as do non-smokers and heavy smokers (>15 cigarettes per day) have an even higher incidence of breakthrough bleeding.

Missing pills is an obvious cause of breakthrough bleeding. Missing one pill only slightly raises the incidence of bleeding but by the time 3 pills are missed, over 80% of women will have some bleeding if not a full menses. Many women who miss pills (noncompliance) fail to tell their doctors about that and as a result may undergo therapies and changes in pills that are not really needed when in fact the best therapy would be to do nothing but take the pills more regularly. From 25-33% of women miss more than one pill in a cycle.

How is intermenstrual bleeding on the contraceptive pill best treated?

The best treatment in the first 3 cycles of pill use is just reassurance that the bleeding problems are very likely to decrease and disappear with continued use. If the bleeding is distressing or continues after 3 months, the best treatment is to take estrogen for 7-10 days during the first part of the cycle to build up the endometrium and make it more resistant to sloughing. Unfortunately most physicians do not try this treatment first but rather switch the brand of pills in hopes that that will decrease bleeding. There actually are no scientific studies that test different strategies to arrest breakthrough bleeding on the birth control pills so we do not really know the best treatment for this.

Do some brands of birth control pills make acne worse?

At the current time there is only one brand of birth control pill that has FDA approval to be used to prevent acne (Ortho Tricyclen®). Truthfully all estrogen containing oral contraceptives decrease sebum production which in turn usually decreases acne. Many studies have shown up to 70% reduction in acne counts on the face, chest, neck and back. Levonorgestrel containing pills tend to decrease acne less than other progestins in pills but overall there still is a reduction even with the more androgenic progestins. The decrease in acne is directly proportional to the decrease in serum testosterone. The pill does this by increasing sex hormone binding globulin which inactivates some of the circulating testosterone.

Some women will develop or have their acne worsen on the pill. In fact acne is is often listed as a side effect of the pills. Studies consistently show about 5% of women develop acne when starting pills.

What is the best regimen for taking oral contraceptives?

There are several principles that improve oral contraceptive compliance:

  • Women should develop a daily routine for taking pills so that each day, taking pills will be as regular as brushing their teeth. Women without a daily routine forget or miss pills 3 times more than those with a daily routine.
  • Be familiar with the literature included with the pills. Know about how the pills work and what to expect when first starting the pills.
  • Know what to do if a pill is missed. Take the missed pill or pills as soon as you remember and then continue on to finish the pack if full menstrual bleeding has not started. If bleeding the equivalent of menses has started, just wait as if you finished the pills and start a new pack of active pills after being off 5-7 days. Use back up contraception if you miss more than one pill.
  • Plan a backup contraceptive method. Be prepared with condoms and foam or indulge in abstinence until being back on the active pills for one week.


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