Pregnancy on Birth Control

Although many birth control methods are highly effective, you can still get pregnant while using them. Studies suggest that around half of all unintended pregnancies happen when birth control is used.

While it is possible that the failure may be product-related, certain behaviors can undermine the effectiveness of birth control, including the inconsistent use of hormonal contraceptives or the improper use of condoms.

Education can help overcome these concerns. This not only includes learning how to use birth control correctly but also having a greater understanding of pregnancy and contraception—such as when ovulation occurs and how long sperm can live inside the vagina after sex.

This article offers essentials on the risk of pregnancy, the effectiveness of different birth control methods, and the 20 most common reasons for failure.

A woman distraught by a failed pregnancy test
Yuri Arcurs / Collection: E+ / Getty Images

Gender Definitions

For the purpose of this article, "male" refers to people born with penises, and "female" refers to people with vaginas irrespective of whether they identify as one or several genders or no gender at all.

How Pregnancy Works

Sometimes a couple will experience unintended pregnancy because they have misconceptions as to when fertility is possible. The process of pregnancy is directed by a roughly 28-day menstrual cycle:

  • Day one is the first day of your period.
  • Around day 14, ovulation occurs. This is when a mature egg is released from one of the ovaries.
  • Within 24 hours of ovulation, sperm released during vaginal intercourse can find their way to the egg and fertilize it (referred to as conception).
  • About six days after fertilization, the fertilized egg will implant itself into the lining of the uterus (womb).
  • Around day 21, if conception and implantation have occurred, you are pregnant.

However, it may take another five to seven days for a pregnancy test to return a positive result.

When Can Conception Occur?

During the average menstrual cycle, there are seven days when an egg is able to be fertilized. This "fertile window" consists of five days before ovulation, the day of ovulation, and the day after.

Timing when ovulation will occur can be tricky since it doesn't always happen at the same time every month. Research suggests that people who consistently have periods every 26 to 32 days are most likely to conceive from days 8 to 19. That is a time span of 10 days.

The expanded period is due to the fact that sperm can live inside the female body for up to five days. So even if you do not ovulate for another four days after sex, sperm could still be living inside you that can fertilize an egg.

Types of Birth Control

There are hormonal and non-hormonal birth control methods that can prevent pregnancy, some of which can be used in combination.

Hormonal birth control methods are those that interfere with the menstrual cycle and ovulation. These generally need to be used consistently on an ongoing basis.

Non-hormonal methods involve barrier devices or sexual practices that prevent sperm from reaching the egg. Many barrier methods can be used on demand.

20 Reasons Why Birth Control Fails

There are many reasons why birth control fails. The main reason is user error.

The top 20 causes of birth control failure include:

  1. You're off on your timing with the rhythm method.
  2. There is pre-ejaculate ("pre cum") in the vagina when using the withdrawal method.
  3. You put on a condom incorrectly.
  4. You use condoms inconsistently.
  5. An incorrectly sized condom breaks or slips off during intercourse.
  6. You use an expired condom.
  7. You use an oil-based lubricant on a latex condom.
  8. You don't use enough spermicide.
  9. You don't put enough spermicide in the vagina.
  10. You don't take the pill or minipill at the same time every day.
  11. You miss doses of the pill or minipill.
  12. You miss getting a Depo Provera shot every three months.
  13. A diaphragm or sponge is incorrectly placed.
  14. The NuvaRing is not replaced within three hours of falling out and you have sex.
  15. The NuvaRing is used for more than four weeks.
  16. You don't replace an IUD on schedule.
  17. An IUD moves out of place.
  18. You take medications that interfere with the effectiveness of certain hormonal contraceptives.
  19. Your weight is affecting the effectiveness of certain hormonal contraceptives.
  20. You take the morning-after pill more than five days after condomless sex.

Using alcohol and drugs can also affect your judgment and cause you to use birth control incorrectly or not at all.

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. While there are many reasons why you may have missed your period, the most common cause is pregnancy.

The only way to know for sure if you're pregnant is to get a pregnancy test. Even so, you need to test at the right time and not too early.

Because it can take a minimum of six days for your body to produce enough human chorionic gonadotropin (hCG) to register an accurate result, testing too early can lead to a false negative result.

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

If you have had condomless sex, or know that your birth control failed within the last five days, emergency contraception may still be able to prevent unintended pregnancy.

Summary

It is possible to get pregnant on birth control. Most birth control failures are the result of user error, whether it is using birth control incorrectly or using it inconsistently. This is true for both hormonal and non-hormonal contraceptives. Correcting these errors can better ensure you avoid pregnancy.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Guttmacher Institute. Unintended Pregnancy in the United States.

  2. Su RW, Fazleabas AT. Implantation and establishment of pregnancy in human and nonhuman primates. Adv Anat Embryol Cell Biol. 2015;216:189-213. doi:10.1007/978-3-319-15856-3_10

  3. Gnoth C, Johnson S. Strips of hope: accuracy of home pregnancy tests and new developments. Geburtshilfe Frauenheilkd. 2014;74(7):661-669. doi:10.1055/s-0034-1368589

  4. Sakkas D, Ramalingam M, Garrido N, Barratt CL. Sperm selection in natural conception: what can we learn from Mother Nature to improve assisted reproduction outcomes? Hum Reprod Update. 2015;21(6):711-726. doi:10.1093/humupd/dmv042

  5. Centers for Disease Control and Prevention. Contraception: how effective are birth control methods?

  6. American Pregnancy Association. Birth control failure.

  7. American Pregnancy Association. hCG (human chorionic gonadotropin): the pregnancy hormone.

By Dawn Stacey, PhD, LMHC
Dawn Stacey, PhD, LMHC, is a published author, college professor, and mental health consultant with over 15 years of counseling experience.