Did My Birth Control Fail?

Getting Pregnant on Birth Control

Did My Birth Control Fail?. Yuri Arcurs/Collection: E+/Getty Images

Even though there are many birth control methods that are very effective, you can still get pregnant while on birth control. About half of all unintended pregnancies actually happen when you are using birth control. So certain conditions or behaviors can increase the chances that your birth control won’t be as effective at preventing pregnancy. If you have experienced birth control failure (like a condom breaking), or your period is late, you may be wondering, did my birth control fail?

Remember: If you have had unprotected sex or know that your birth control failed (within the last 5 days), know that emergency contraception may still be able to prevent an unintended pregnancy.

To undertand how getting pregnant on birth control can happen, it's helpful to have an understanding of how the female body works.

How the Female Reproductive System Works

If it has been more than 5 days since you have missed a period and believe that your birth control may have failed, let's examine your female reproductive system, so we can understand when pregnancy actually begins.

  • In most females, about once a month, several eggs mature, and one is released from the ovary (known as ovulation).
  • Up until this time, the lining of the uterus has become thick so it can act as a “nest” for the egg.
  • Once the egg is released, if it is not fertilized within 12 to 48 hours, it disintegrates.
  • Approximately 2 weeks later, the thick lining of the uterus is shedthis is what causes a period.
  • Your menstrual cycle then begins again (on the first day of your period).


Ovulation typically occurs around 14 or 15 days from the first day of the female's last menstrual cycle. It is important to note, though, that there could be great variation in ovulation times. Factors such as stress and diet can all affect when you ovulate.

Timing ovulation can also be tricky since it may not always happen at the same time each month. In general, research suggests that for women who consistently have periods every 26 to 32 days, conception (getting pregnant) is most likely to occur during days 8 to 19. When counting the days of your menstrual cycle, you should count the day that your period starts as Day 1. Once ovulation takes place, the egg travels into the fallopian tube and is available to be fertilized by a sperm.

Your most likely time to be getting pregnant is when you are ovulatingbecause this is when you are most fertile. If you have sex around the time that you are ovulating, you are more likely to get pregnant. So, if a couple has unprotected intercourse, they should be most “careful” during the five days leading up to ovulation and one day after it. This is because sperm can live inside the female body for up to five days. So even if you do not ovulate for another four days after having sex, sperm could still be living inside you that can fertilize your egg when it is released.

  • If you believe that your birth control may have failed around this time frame, you could be at greater risk for an unplanned pregnancy.

    Getting Pregnant

    The medical community says that pregnancy begins with implantationthis is when the fertilized egg implants into the wall of your uterus. This actually occurs several days after the sperm fertilizes the egg. The human chorionic gonadotropin (hCG) hormone is only produced once a fertilized egg implants in the uterus. In most women, this happens about 6 days after conception. The hCG levels increase significantly with each passing day. Pregnancy tests measure whether or not hCG is present. Because it can take a minimum of 6 days after conception for your body to produce hCG, taking a pregnancy test too early may give you a false negative result (meaning, you are, indeed pregnant, it was just too early for the test to detect the hormone).

    Studies indicate that most pregnancy tests will provide accurate results if you take the pregnancy test one week after your missed period.

    Am I Pregnant - Did My Birth Control Fail?

    Thinking that you may have gotten pregnant while on birth control and do not want to be can be stressful. To add to the confusion, many early pregnancy signs can also be due to other reasons. But, in general, the most common cause of a missed period is pregnancy. It is also important to note that many women who are pregnant may have spotting or staining right around the time they are expecting a period.

    Hormones can complicate the issue further. When your period is just late (meaning not due to pregnancy), your body may just be affected by premenstrual anxiety (anxiety, associated with PMS, that occurs before you have your period). Also, if you begin to stress about a missing period, you can further prevent your period from coming. On the flip side, if you are pregnant, hormones associated with pregnancy can make you feel obsessed.

    Getting Pregnant on Birth Control

    There are many reasons that getting pregnant on birth control is possible. The main reason is user error. Examples of this include not properly using your birth control (according to it's instructions) and/or not always using your birth control. The condom you used may have broken or maybe you missed too many birth control pills. Other reasons that you may get pregnant while on birth control include:

    So, you see, it is very possible to get pregnant while on birth control. But keep in mind that these typical user errors are factored into the failure rate of each birth control method. When you look at these rates, you typically see two numbers. The higher number is the effectiveness with perfect use and the lower number is the effectiveness with normal use (which includes these common errors). So, even though getting pregnant on birth control can happen, the chances that it does are still fairly low. And don't worry, if you do get pregnant while on the pill (without realizing it), continuing taking the pill while pregnant will not harm your baby.

    To Determine if Your Birth Control Failed

    The best way to know if you have gotten pregnant while on birth control is to figure out if you have missed your period. To help you determine if your period is considered “late,” according to Dr. Kathleen Mammel, Clinical Assistant Professor of Adolescent Medicine at University of Michigan in Ann Arbor:

    • “A menstrual cycle is the period of time from day one of your menstrual period to day one of your next period. Menstrual cycles vary in length from one woman to the next. They may occur at the same time each month or be irregular. Typically, a cycle occurs about once a month, but can be as short as 21 days or as long as 35 days and still be considered normal. Menstrual flow lasts about 3 to 7 days. A menstrual period is considered late if it is 5 or more days overdue according to your usual pattern of periods. A period is considered missed if there is no menstrual flow for 6 or more weeks.”

    So, before you begin to officially worry if your birth control may have failed, it is a good idea to first confirm whether or not you are pregnant. The best and most reliable way to determine if your birth control failed and you have gotten pregnant while on birth control is to take a pregnancy test.

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