Can You Get Pregnant While on Birth Control?

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pregnant-244662_640Birth control methods have been present since the ancient times. Historical data suggests that in 1500 BC, ancient Egyptian women use chemical contraception in the form of a vaginal suppository composed of sodium bicarbonate, honey and crocodile dung. Fortunately, modern measures of preventing unintended pregnancies have evolved with scientific proof leading to its widespread use. World Contraceptive Data of the United Nations states that 64% of all married women use contraceptives. In the United States alone, research suggests that almost all sexually active women have used contraception at some point in their lives. At present, several birth control methods are in use by women in the reproductive age group.

Types of Birth Control and How They Work

Depending on how they are used, contraceptive methods are categorized in four groups. These are intrauterine contraception, hormonal methods, barrier methods and fertility-awareness based methods.

Intrauterine contraception involves the instillation of a device within a woman’s uterus to prevent pregnancy. Common devices available in the market are the Copper-T intrauterine device and Levonorgestrel intrauterine system. Copper-T IUD has the advantage of remaining within the uterus for 10 years, while Levonorgestrel IUD can stay up to 5 years. A certified health professional instills the device on a clinic follow up.

Hormonal methods involve the use of chemical derivatives that alter the reproductive cycle to prevent fertility. These can be administered in various forms, such as orally ingestible pills, injectable medications, implants, dermal patches and vaginal rings. Birth control pills rely on instructional compliance of the end user to deliver its effectiveness. Hormonal implants are inserted dermally on the upper arm and can last up to three years. Injectable hormones are administered every three months to ensure contraception. Hormonal patches are applied once a week for three weeks then removed on the fourth week. Vaginal rings are likewise worn for 3 weeks then removed on the fourth week to allow menstruation to occur.

Barrier methods as the name implies, involves the use of a device to mechanically block the entry of sperm into the vaginal canal. These come in the form of cervical caps, condoms (male and female) and spermicides. Prior to sexual intercourse, cervical caps and female condoms are placed within the vagina for contraception. Male condoms are worn to prevent sperm from entering the vaginal canal. Spermicides chemically kill the sperm cells. These are placed within the vaginal vault prior to intercourse and up to eight hours after. These are available in several forms such as gels, creams and foams.

Fertility-awareness based method is a natural family planning method that relies on the predictability of a woman’s fertility period. This does not involve the use of any special device. Sexual partners abstain once a woman is presumed to be in the fertile period. The ovulation period is determined by utilizing the calendar method or by determining a woman’s basal body temperature. Women with regular menstrual cycles usually use this method since they have a foreseeable fertility period. It has the advantage of being spared from possible side effects of other contraceptive methods.

Birth Control Failure

Pregnancy is possible even if a woman is on birth control. This accounts for birth control failure, which is observed in approximately half of unintended pregnancies. Several factors have been described that may interfere with the efficacy of birth control methods.

Compliance to Instructions

Contraceptive methods that interfere with the reproductive cycle require strict adherence to instructions for it to be effective. Skipped pills and failure to properly administer medications could potentially lead to decreased effectiveness, and ultimately failure. According to research, in the United States, 43% of unintended pregnancies are due to inconsistent and incorrect use of contraceptive methods.

Interference With Other Medications

Certain medications may decrease the overall effectiveness of oral contraceptives that may interfere with drug level concentration in the blood or its pharmacologic action. Commonly used anti-seizure medications such as Phenytoin and Phenobarbital interfere with the metabolism of birth control pills. Other drug classes that are known to interfere with contraceptive medications are broad- spectrum antibiotics, antivirals and thyroid medications. When selecting a contraceptive method, women should tell their health care providers of their current medications for the proper choice of a contraceptive method.

Inherent Contraceptive Failure Rate

Despite proper use and strict compliance to contraceptive method instructions, some women still get pregnant. This is due to inherent contraceptive failure rate. As an example, research study show that up to 8% of women who use diaphragm accidentally get pregnant within one year of use. Fertility-awareness based methods have an inherent failure rate of up to 4.8% despite strict compliance to standard days or calendar method. Majority of oral contraceptive pills have an inherent failure rate of less than 1 percent, granting that users are strictly adherent to product specifications.

Obesity and Chronic Illness
Obesity causes significant physiologic changes in the body compared to non-obese people. These changes may affect the way drugs are absorbed and distributed within the body. This may potentially cause a failure in contraception. Women with chronic illnesses such as diabetes and hypertension are challenging patients to the reproductive healthcare team. Most of them are taking various medications, which interfere with birth control medications.
Most birth control methods have a low failure rate if used properly. However, despite modern contraceptive methods, absolute prevention of pregnancy has not yet been achieved. Consult with a certified health care provider for appropriate selection of a birth control method may potentially decrease the chances of unintended pregnancy.

Author: Marinelle C

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References :

+ Centers for Disease Control and Prevention. (2016). Contraception. Retrieved June 16, 2016, from


+ Frost JJ, Darroch JE. Factors associated with contraceptive choice and inconsistent method use, United States, 2004. Perspect Sex Reprod Health. 2008;40:94–104.

+ Gibson, M. (2015, February 2). The Long, Strange History of Birth Control. Time Magazine.

+ Mittal, P., Dandekar, A., & Hessler, D. (2014). Use of a Modified Reproductive Life Plan to Improve Awareness of Preconception Health in Women with Chronic Disease. The Permanente Journal, 18(2), 28–32.

+ Robinson, J. A., & Burke, A. E. (2013). Obesity and hormonal contraceptive efficacy. Women’s Health (London, England), 9(5), 453–466.

+ Shoupe, D., & Mishell, D. R. (2006). The handbook of contraception: A guide for practical management. New York: Humana Press.


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