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Why Would a Woman Become Pregnant While Using Birth Control?

Unexpected pregnancies can happen while using birth control. Sometimes, this is due to user error. At other times, the method itself fails. Reduce your risk of an unplanned pregnancy by using your birth control correctly. Different methods of contraception have different types of problems.


Contraceptives can function in any of several ways. Barrier methods block sperm from reaching the uterus with a physical barrier. Chemical contraceptives or spermicides kill sperm. Hormonal birth control, including the birth control pill, NuvaRing and the birth control patch, alter a woman’s hormones to prevent ovulation or implantation.

Failure Rates

Statistics describing birth control failure rates typically include figures for perfect use as directed and for actual use. Perfect use implies no user error, while actual use can include both error and a total failure to actually use the contraceptive. For instance, the Contracept website says that condoms used perfectly have only a 2 percent failure rate, while actual use failure rates are around 15 percent. Oral contraceptives are 99.7 percent effective if taken as directed, every day; however, around 8 percent of women taking the birth control pill become pregnant each year. Some birth control failures are preventable, while others are not.

Hormonal Contraceptives

Hormonal birth control is quite effective when used properly. Unplanned pregnancies may result if birth control pills are missed, skipped, or if illness causes vomiting shortly after taking the pill. Pregnancy may also result if a back-up method of contraception is not used the first cycle on hormonal contraception or when taking antibiotics.


Condoms are the most accessible and convenient contraceptive choice for many people. With perfect use, condoms are a good birth control choice. Condoms may fail or break, leading to unplanned pregnancy, if they are expired or have been exposed to extreme temperature variations. Condom breakage is also more likely if two condoms are used instead of one or if the condom fits poorly.


There are several ways to reduce the risk of an unplanned pregnancy while using birth control. Consider using not one, but two contraceptive methods. Pair condoms with a spermicide or use condoms to back up hormonal birth control. In the event of birth control failure, visit a local pharmacy and purchase the morning-after pill. According to Planned Parenthood, the morning after pill will prevent up to 89 percent of unplanned pregnancies.

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