Oral Contraceptives: Benefits and Risks
Since they were first introduced in the 1960s, the birth control pill ("the pill") has been a popular and extremely effective form of contraception. The pill is easy to use and when taken correctly, it is 95% to 99.9% successful at preventing pregnancy. But its use has been associated with a number of worrisome side effects. Early research indicated that women taking the pill risked increased rates of heart disease, blood clots, stroke, and breast cancer.
Luckily, the picture has improved greatly since those early days. Drug companies have developed new low-dose birth control pills that contain lower levels of estrogen and decrease the risk of unwanted side effects. Furthermore, not only have the risks decreased, but extensive research over the past twenty years has also shown that there are many real benefits to using the pill that reach far beyond contraception. This article contains an update on the most significant of these benefits and risks.
Findings From the Women’s Health Initiative
Because of the cardiovascular risks associated with early birth control pills, research has continued to focus on this area. Most of this research has found that women using the pill have a slightly elevated risk of heart disease, blood clots, and stroke. The risks have decreased significantly with the advent of the low-dose pill, but remain particularly high for women who smoke, have high blood pressure, or diabetes.
T he Women’s Health Initiative (WHI) study is turning this fairly established wisdom on its head. In October 2004, at the annual meeting of the American Society of Reproductive Endocrinology, Rahi Victory, MD, of the Wayne State Medical School in Detroit, Michigan, presented preliminary findings from data on the group of more than 160,000 women participating in the study. These women were between the ages of 50 and 79 at the time the study began, and about one third (67,000) reported using oral contraceptives at some point in their lives.
Contrary to earlier studies, Dr. Victory found that women who used oral contraceptives actually had about an 8% lower risk of developing cardiovascular disease than non-users. Decreases occurred in the rates of stroke, heart attacks, high blood pressure, and high cholesterol levels. Moreover, the longer birth control pills were used, the larger were the reductions in risk. There were some findings, however, that mirrored those of other studies; increasing age, smoking, diabetes, and being overweight significantly increased the risks of heart and circulatory problems in women who used the pill.
It should be noted that because this study was designed to test the effects of hormone replacement therapy in postmenopausal women, there are numerous flaws and bias problems in using the data. The quality of this evidence is too poor to determine whether or not oral contraceptives provide a protective effect against cardiovascular disease.
Reduced Risk of Ovarian and Endometrial Cancers
Although Dr. Victory’s study is far from conclusive at this point, additional studies have established clear benefits to using oral contraceptives for several health issues other than heart health. Most promising of these, perhaps, is the pill’s strong protective power against certain types of cancer, particularly cancers of the ovaries and endometrium (the lining of the uterus).
Ovarian cancer is a relatively rare cancer, but because it is infrequently diagnosed in its early stages, it remains the most fatal type of gynecologic cancer. Oral contraceptives provide a powerful protective effect against this cancer, reducing a woman’s overall risk by 40% to 80% if they are taken for more than five years duration. Although the exact mechanism of this protective effect is not yet understood, it is most likely related to the suppression of ovulation. The reduction in risk increases with the duration of use and lasts for at least ten years after the pill is discontinued. Because ovarian cancer tends to occur in the peri- and post-menopausal years, the long-term protection provided by oral contraceptives is good news for older women who used the pill earlier in life.
Endometrial cancer is a more commonly occurring but less fatal cancer. Again, birth control pills have been found to decrease the risk of this cancer by 50% to 72%, with protection increasing with the length of time on the pill. This protective effect continued long after the pill was discontinued (up to 20 years in one study).
Other Benefits of the Pill
In addition to reducing risk of ovarian and endometrial cancers, studies have confirmed the following healthful “side effects” of using the pill:
- Reduced risk of ectopic pregnancies (ie, pregnancies that occur outside the uterus, particularly in the fallopian tubes)
- Reduced risk of developing iron-deficiency anemia
- Reduced menstrual flow, heavy bleeding, irregular periods, and painful cramps
- Protection against pelvic inflammatory disease (PID)
Because oral contraceptives prevent ovulation, they significantly reduce the risk of both unwanted pregnancies and pregnancies that occur outside the uterus (ectopic pregnancies). The pill also reduces menstrual flow, which results in fewer problems with cramps and heavy bleeding, and helps to prevent the development of anemia. Finally, the thick cervical mucous fostered by the progestin in pills creates a barrier to both sperm and to bacteria, providing protection from pelvic infections. However, it is important to remember that the pill provides no protection against HIV or other sexually transmitted diseases.
Other research has found oral contraceptives to be helpful in:
Breast Cancer and the Pill
Research has shown conflicting results regarding breast cancer among women using oral contraceptives. Some studies have shown a very small increase in risk, but there are questions as whether this increase is real or the result of earlier detection based on the regular office visits required of pill users. The increased risk endured for approximately 10 years after ceasing usage, and then disappeared. Additional research is needed to clarify the actual risks involved.
Do the Benefits Outweigh the Risks?
The decision as to which, if any, type of birth control to use is a highly personal one that a woman should make after consultation with her doctor. But research over the past twenty years has established that for most women, birth control pills offer a safe and effective option for contraception. Risks of complications are quite small for the most part, and benefits are surprisingly wide ranging. Only for women who smoke, have diabetes, or high blood pressure do the risks appear to sometimes outweigh the benefits. Still, women may be troubled that in July 2005 the prestigious International Agency for Research on Cancer (IARC) has classified birth control pills as a “group 1” human carcinogen. The US National Cancer Institute has created a website detailing the cancer-related benefits and risks of contraceptives (see reference below). Women who want comprehensive information on what is (and what is not) known about the cancer risks and benefits of oral contraception would do well to read through the available information and then make up their own minds. Very few doctors share the IARC’s viewpoint or even completely understand its logic.
American College of Obstetricians and Gynecologists
Planned Parenthood Federation of America, Inc.
Population Reports, Johns Hopkins School of Public Health
The Society of Obstetricians and Gynaecologists of Canada
Women's Health Matters
Burkman R. Oral contraceptives: Current status. Clinical Obstetrics and Gynecology. 2001;44(1):62-72.
Burkman R, Schlesselman JJ, Zieman M. Safety concerns and health benefits associated with oral contraception. Am J Obstet and Gynecol. 2004;190:S5-S22.
Jensen JT, Speroff L. Health benefits of oral contraceptives. Obstet and Gynecol Clinics of North Am. 2000;27(4): 705-721.
Victory R, et al. Adverse cardiovascular disease outcomes are reduced in women with a history of oral contraceptive use: Results from the Women’s Health Initiative Database [abstract]. Fertility and Sterility. 2004;82(2):0-130.
IARC monographs programme finds combined estrogen-progestogen contraceptives and menopausal therapy are carcinogenic to humans. International Agency for Research on Cancer; July 29, 2005. Available at: http://www.iarc.fr/ENG/Press_Releases/pr167a.html#Group1.
Fact sheet: Oral contraceptives and cancer risk. National Cancer Institute website; May 4, 2006. Available at: http://www.cancer.gov/cancertopics/factsheet/Risk/oral-contraceptives.
Schneider HP, Mueck AO, Kuhl H. IARC monographs program on carcinogenicity of combined hormonal contraceptives and menopausal therapy. Climacteric. Dec 2005;8(4):311-316.
Last reviewed June 2008 by Ganson Purcell Jr., MD, FACOG, FACPE
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
Copyright © 2011 EBSCO Publishing All rights reserved.