Birth Control
How Do Contraceptives Work?
Contraceptives are methods of preventing or ending pregnancy, also referred to as “birth control”, and work in three ways: preventing fertilization, preventing implantation, and altering a woman’s body chemistry to prevent ovulation.
1. Prevent Fertilization
Fertilization is the union of a man’s sperm and woman’s egg. Some contraceptives create a physical barrier to block sperm from reaching an egg. Male and female condoms and the diaphragm are examples.
2. Make the Uterus Hostile to Implanation1
Contraceptives can attempt to prevent a baby from implanting in the mother’s uterus after fertilization by creating a hostile environment. Intra-uterine Devices (IUDs) and chemical methods are in this category.
3. Alter Body Chemistry2
Typically referred to as “hormonal” contraceptives, synthetic steroids like the pill mimic hormones to prevent pregnancy by changing a woman’s body chemistry, which has three impacts:
Prevent ovulation, the release of the egg each menstrual cycle.
Produce less and thicker mucus in the cervix so that sperm cannot easily enter the uterus.
Thin the lining of the uterus, making it more difficult for a fertilized egg to implant.
Chemical contraceptives include the oral birth control pill, Depo-Provera injection, patch, and implant. Chemical methods provide no protection against STDs and can actually increase your risk of getting an STD by making your reproductive tract more vulnerable to infection (see Birth Control and STDs).
Is There Really Such a Thing as Safe Sex?
Despite the advocacy of condom use to reduce your risk of acquiring an STD, the Centers for Disease Control (CDC) states, “there’s no absolute guarantee even when you use a condom”. Even the CDC does not embrace the term safe sex, calling it “less risky” sex instead.3 Condoms and HIV
What they also fail to mention is what “risky” really means. As determined by the National Institutes of Health, “overall, the condom’s effectiveness at preventing HIV transmission is estimated to be 87%, but it may vary between 60% and 96%”.4 These numbers don’t even factor in the element of exposure over time.
In an International Planned Parenthood Federation Medical Bulletin, author Willard Cates states that, “the risk of contracting AIDS during so-called ‘protected sex’ approaches 100 percent as the number of episodes of sexual intercourse increases.” According to the graph submitted by Cates below, you will inevitably, eventually contract HIV/AIDS when having sex with an infected partner, even with perfect condom use.
Graph shows Risk (of contracting HIV) vs. Exposure (the number of sexual encounters)
Note how the right side of the ellipse (“protected sex”) rises to meet the left (“unprotected sex”) at a point which represents 100% risk.5
HIV is one of over 25 sexually transmitted infections that can have a serious impact on your future reproductive and overall health, especially if left untreated. Pregnant women are particularly at risk. The only way to avoid contracting a potentially deadly infection is to abstain from sexual activities with anyone who may be carrying an infection.
Find out more about common STDs and their related conditions on the Center for Disease Control and Prevention’s website.
Concerned about your sexual or reproductive health? Schedule your free consultation with Care Pregnancy Clinic.
Contraceptive Effectiveness & Side Effects
- Male Condom
- Female Condom
- Diaphragm or Cervical Cap
- Birth Control Pill
- Depo-Provera Shot
- The Patch
- Implant/IUD
The Truth About Oral Contraceptives
Providers often will not furnish a full range of facts when prescribing Combined Oral Contraceptives (COC), basing the information given on their own professional opinion rather than a well-balanced presentation of the data available. Ultimately, it’s your responsibility to read the fine print.
Brain Cancer and “The Pill”
A recent study published in the British Journal of Clinical Pharmacology27 (BJCP) aimed to prove that “oral contraceptive use influences the risks for certain cancers.” Results concluded that long-term use may increase the risk of gliomas, tumors that occur in the brain and spinal cord. This comes as a surprise to many since estrogen and progestin were originally believed to protect against gliomas.28
Andersen and colleagues assessed over 2,000 women ages 15 to 49 diagnosed with gliomas based on their exposure to estrogen-progestagen and progestagen-only contraceptives. The study reveals that women increase their risk of gliomal brain cancer by 50% if they ever use hormonal birth control, and by 90% if they use it long-term (5 years or more).29
Named for their origin, gliomas effect the glial cells which surround and support neurons in the brain. Gliomas account for only 10% of all cancers; however, they also account for 80% of all malignant brain tumors30 and have a mere 15% survival rate.31
The bottom line is that use of synthetic hormonal agents like the birth control pill can have lasting effects on a woman’s body. Make sure that you have all of the facts you need about pregnancy prevention and your future health before you swallow The Pill. The Suggested Advantage of IUDs: Have the Risks Changed or Just Our Perception?
In an attempt to “curb teen pregnancy,”32 Golisano Children’s Hospital recently launched a campaign to promote the benefits of IUDs (intrauterine devices) over other forms of birth control.
IUDs are T-shaped plastic devices with a string attached and come in two types: hormonal and copper. Neither of the two types of IUDs prevent ovulation. Instead, they deter sperm from reaching the unfertilized egg. Copper IUDs do this by releasing a small amount of copper into the uterus, which is believed to immobilize the sperm. Hormonal IUDs release a small amount of progestin similar to progestin-only birth control pills. This causes the cervical mucus to thicken, making it difficult for sperm to pass. It also causes the uterine lining to thin, creating an uninhabitable environment for a fertilized egg, thus forcing it to be aborted prematurely.
According to Dr. Greenberg, an adolescent medicine specialist at the hospital, “Today’s [IUDs] are safe, effective, invisible, and can be easily removed with no lingering effects when you decide to become pregnant.” Dr. Aligne of the Hoekelman Center goes on to say, “There’s been a lot of research about how these devices are safe for teens. But some myths from several decades ago persist, and even some doctors don’t have all the updated information.”33
However, a recent study (Sept. 2014) published by the Journal of Research in Medical Sciences34 continues to confirm that IUDs are associated with an increased risk (OR=4.39) of ectopic pregnancy. The fetal mortality rate for an ectopic pregnancy is 100%, and although available treatment methods have improved, the negative risk to future fertility is still very much a factor. Having a single ectopic pregnancy significantly lowers a women’s chances of becoming pregnant again (up to 33%),35 and also increases her risk of having additional ectopic pregnancies.
If you’re thinking about an IUD, talk to your doctor about the risks of ectopic pregnancy.
Nearsighted? Birth Control May Escalate Vision Problems
According to the American Society of Health System Pharmacists36, near-sighted women who begin taking oral contraceptives at or near puberty experience a greater loss in vision due to the estrogen-progestin pill’s potential to significantly change the shape of the cornea. Resulting issues include advanced myopia, astigmatism and Keratoconus.
Myopia by nature progresses through adolescence and plateaus in adulthood. However, in women who develop myopia (near-sightedness) at or near puberty, which in females is between the ages of 9 and 1437, oral contraceptives produced marked advancement in myopia, up to 3 times the refractive error. Refractive error is the misshaping of the cornea which causes symptoms including blurred vision, double vision, haziness, glare or halos around bright lights, squinting, headaches, or eye strain38.
Astigmatism (football-shaped cornea), a common issue which can be amended with corrective lenses, was also increased in those with a history of the ocular disorder. Those with astigmatism also had the potential to develop Keratoconus (cone-shaped cornea). Severe changes in cornea shaping caused by these issues can eliminate the option to wear contact lenses as corrective eyewear.
With less than 2% of females having had sex by the age of 12 and 16% by the age of 1539, eye health in relation to oral contraceptives is a growing concern. In a study conducted by the British Heart Foundation, it was reported that the percentage of 10 and 11-year olds who experienced some degree of myopia were as follows40:
2% Asian descent
0% African descent
4% Non-Hispanic Whites
It’s important to know your full health history before beginning any oral medication and be sure to get all of the facts about your birth control pill. Emergency Contraception
Levonorgestrel, marketed as Plan B® One-Step and Next Choice®, is classified as an “emergency contraceptive,” and is commonly referred to as “the morning after pill.” It is approximately a 50x dose of the progesterone-only oral birth control pill designed for daily use.
How It Works
- Prevents ovulation if it has not yet occurred.
- Thickens cervical mucus, making it more difficult for sperm to enter the uterus.
- Changes the lining of the uterus to prevent a baby from implanting and developing, should fertilization occur. 41
Risks and Side Effects
Common side effects include:
- Heavier menstrual bleeding
- Nausea
- Lower abdominal pain
- Fatigue
- Headache
- Dizziness
- Breast tenderness
- Delay of menses by more than one week
Levonorgestrel is classified as “possibly carcinogenic to humans.” It has been shown to increase risk of cancer in animals. 42
If you’re concerned that you may be pregnant or would like to discuss your options with a nurse, please contact us or schedule an appointment online.
Medically Reviewed By:
Tessa, NP
Staff Nurse Practitioner, Baton Rouge
1 Finer, L.B., Henshaw, S.K., (2006). Disparities in rates of unintended pregnancy in the United States, 1994 and 2001. Perspect Sex Repro H; 38(2): 90-96.
2 Centers for Disease Control and Prevention (2020). Contraception. Retrieved June 2021 from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
3 The American College of Obstetricians and Gynecologists (2011). How to prevent sexually transmitted diseases. FAQ009.
4 Centers for Disease Control and Prevention (2020). Contraception. Retrieved June 2021 from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
5 Centers for Disease Control and Prevention (2020). Contraception. Retrieved June 2021 from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
6 Rosenberg, M.J., Davidson, A.J., Chen, J.H., Judson, F.N., Douglas, J.M., (1992). Barrier contraceptives and sexually transmitted diseases in women: a comparison of female-dependent methods and condoms. Am J Public Health; 82(5):669-674.
7 Centers for Disease Control and Prevention (2020). Contraception. Retrieved June 2021 from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
8 Rosenberg, M.J., Davidson, A.J., Chen, J.H., Judson, F.N., Douglas, J.M., (1992). Barrier contraceptives and sexually transmitted diseases in women: a comparison of female-dependent methods and condoms. Am J Public Health; 82(5):669-674.
9 Lidegaard, Ø., Løkkegaard, E., Jensen, A., Skovlund, C.H., Keiding, N., (2012). Thrombotic stroke and myocardial infarction with hormonal contraception. N Engl J Med; 366(24): 2257-2266.
10 Andersen, L., Friis, S., Hallas, J., Ravn, P., Kristensen, B.W., Gaist, D. (2014). Hormonal contraceptive use and risk of glioma among younger women: a nationwide case-control study. Br J Clin Pharmacol; 79(4): 677-684.
11 International Agency for Research on Cancer (1999). Hormonal Contraception and Post-Menopausal Hormonal Therapy. IARC Monogr Eval Carcinog Risks Hum; 72: 288-294.
12 American Society of Health System Pharmacists (2010). AHFS Drug Information 2010: Bethesda; MD, p. 3112.
13 Centers for Disease Control and Prevention (2020). Contraception. Retrieved June 2021 from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
14 Bigrigg, A., Evans, M., Gbolade, B., Newton, J., Pollard, L., Szarewski, A., Thomas, C., Walling, M., (2000). Depo Provera. Position paper on clinical use, effectiveness and side effects. Br J Fam Plann; 26(1): 52-53.
15 Centers for Disease Control and Prevention (2012). Contraception. Retrieved from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
16 Lidegaard, Ø., Løkkegaard, E., Jensen, A., Skovlund, C.H., Keiding, N., (2012). Thrombotic stroke and myocardial infarction with hormonal contraception. N Engl J Med; 366(24): 2257-2266.
17 Centers for Disease Control and Prevention (2020). Contraception. Retrieved June 2021 from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
18 Urbancsek, J., (1998). Nonmenstrual adverse events with Implanon®. Contraception; 58: 109S-115S.
19 World Health Organization & the International Agency for Research on Cancer. (2007). Combined estrogen-progestogen contraceptives and combined estrogen-progestogen menopausal theraby. IARC Monogr Eval Carcinog Risks Hum; 91:1-528.
20 PDR Network (2010). Precise Monagraph. Ortho Tri-cyclen, Mechanism of Action. Retrieved June 2021 from Ortho Tri-Cyclen/Ortho-Cyclen (ethinyl estradiol/norgestimate) dose, indications, adverse effects, interactions… from PDR.net
21 Centers for Disease Control and Prevention (2012). Contraception. Retrieved from www.cdc.gov/reproductivehealth/unintendedpregnancy/contraception.htm
22 Centers for Disease Control and Prevention. (2010). U S. Medical Eligibility Criteria for Contraceptive Use, 2010. Retrieved June 2021 from http://www.cdc.gov/mmwr/preview/mmwrhtml/rr59e0528a1.htm
23 American Cancer Society (2019). Known and Probable Human Carcinogens. Retrieved June 2021 http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/GeneralInformationaboutCarcinogens/known-and-probable-human-carcinogens
24 National Cancer Institute (2018). Oral Contraceptives and Cancer Risk. Retrieved June 2021 from Oral Contraceptives (Birth Control Pills) and Cancer Risk – National Cancer Institute
25 International Agency for Research on Cancer (1999). Hormonal Contraception and Post-Menopausal Hormonal Therapy. IARC Monogr Eval Carcinog Risks Hum; 72: 288-294.
26 NIH, NLM. (2015). Estrogen and Progestin (Oral Contraceptives). Retrieved June 2021 from http://www.nlm.nih.gov/medlineplus/druginfo/meds/a601050.html
27 Andersen, L., Friis, S., Hallas, J., Ravn, P., Kristensen, B.W., Gaist, D. (2014). Hormonal contraceptive use and risk of glioma among younger women: a nationwide case-control study. Br J Clin Pharmacol; 79(4): 677-684.
28 Haghighat, N., Oblinger, M.M., McCandless, D.W., (2004). Cytoprotective effect of estrogen on ammonium chloride-treated C6-glioma cells. Neurochem Res; 29(7): 1359-64.
29 Andersen, L., Friis, S., Hallas, J., Ravn, P., Kristensen, B.W., Gaist, D. (2014). Hormonal contraceptive use and risk of glioma among younger women: a nationwide case-control study. Br J Clin Pharmacol; 79(4): 677-684.
30 Vredenburgh, J.J., Desjardins, A., Reardon, D.A., Friedman, H.S., (2009). Experience with irinotecan for the treatment of malignant glioma. Neuro-Oncology; 11(1): 80-91.
31 Ho, V.K., Reijneveld, J.C., Enting, R.H., Bienfait, H.P., Robe, P., Baumert, B.G., Visser, O., (2014). Changing incidence and improved survival of gliomas. Eur J Cancer; 50(13): 2309-18.
32 Andersen, L., Friis, S., Hallas, J., Ravn, P., Kristensen, B.W., Gaist, D. (2014). Hormonal contraceptive use and risk of glioma among younger women: a nationwide case-control study. Br J Clin Pharmacol; 79(4): 677-684.
33 Haghighat, N., Oblinger, M.M., McCandless, D.W., (2004). Cytoprotective effect of estrogen on ammonium chloride-treated C6-glioma cells. Neurochem Res; 29(7): 1359-64.
34 Andersen, L., Friis, S., Hallas, J., Ravn, P., Kristensen, B.W., Gaist, D. (2014). Hormonal contraceptive use and risk of glioma among younger women: a nationwide case-control study. Br J Clin Pharmacol; 79(4): 677-684.
35 Vredenburgh, J.J., Desjardins, A., Reardon, D.A., Friedman, H.S., (2009). Experience with irinotecan for the treatment of malignant glioma. Neuro-Oncology; 11(1): 80-91.
36 Ho, V.K., Reijneveld, J.C., Enting, R.H., Bienfait, H.P., Robe, P., Baumert, B.G., Visser, O., (2014). Changing incidence and improved survival of gliomas. Eur J Cancer; 50(13): 2309-18.
37 Stöppler, M.C., (2014). Puberty. MedicineNet, Inc. Retrieved June 2021 from http://www.medicinenet.com/puberty/article.htmm/puberty/article.htm.
38 National Institutes of Health (2014). Refractive Errors. Retrieved June 2021 from http://www.nlm.nih.gov/medlineplus/refractiveerrors.html.
39 Finer, L.B., Philbin, J.M., (2013). Sexual initiation, contraceptive use, and pregnancy among young adolescents. Pediatrics; 131(5): 886-891.
40 Rudnicka, A.R., Owen, C.G., Nightingale, C.M., Cook, D.G., Whincup, P.H (2010). Ethnic differences in the prevalence of myopia and ocular biometry in 10- and 11-year-old children: The Child Heart and Health Study in England (CHASE). Invest Ophthalmol Vis Sci; 51(12): 6270-6276.
41 American Society of Health System Pharmacists (2016). AHFS Drug Information: Levonorgestrel. National Institutes of Health. Retrieved June 2021 from http://www.nlm.nih.gov/medlineplus/druginfo/meds/a610021.html.
42 Geneva: WHO IARC (1999) 1972-PRESENT. Monogr Eval Carcinog Risks Hum; p. V72 385.
