Why Are Some Women Able to Get Pregnant While Using Birth Control Pills Correctly?

Women who use birth control correctly don’t want to get pregnant. It isn’t a choice if birth control fails.

Hormonal Systems and Birth Control Pills

Hormonal systems are complex. The early birth control pills bombarded the female reproductive system with hormones, while today's pills are more like guided missiles. Used precisely, they can be remarkably effective but, anything that goes wrong means they will miss the mark.

Reasons for Failure with Perfect Usage

There are a few reasons that birth control pills can fail with perfect usage, but the main problem is that humans are not perfect. If you forget to take the pill for just two days, you can become fertile and remain fertile for up to seven days after you restart taking the pill.

If you’ve ever taken any kind of medication long-term, I can almost guarantee you’ve had the experience of looking in a bottle that should be empty by now and seeing, oops! two pills. If that medicine was birth control, you might be pregnant right now.

Any person could easily make that mistake. But imagine how much harder it would be to never ever forget your pills for 2 or more days if you had a serious illness or injury, had ADHD, or other mental illness, were in an abusive relationship, suffered from poverty, a condition so traumatizing that it causes a temporary loss of IQ points, or had recently experienced a traumatic event or terrible loss, etc.

Effectiveness of Birth Control Pills

Obvious as it is, no prescription medication or any drug is ever 100% effective. You do not have to remember to take or use these methods, and they have no user failure, so they're not less effective with typical use.

Contraceptive Pill

Perfect use: more than 99% effective. Fewer than 1 in 100 women will get pregnant in a year when using the combined pill correctly. Typical use: around 91% effective. Around 9 in 100 women using the combined pill will get pregnant in a year. Perfect use: 99% effective. Around 1 in 100 women will get pregnant in a year when using the progestogen-only pill correctly. Typical use: around 91% effective. Around 9 in 100 women will get pregnant in a year.

Comparison with Other Forms of Birth Control

Birth Control Method Perfect Use Typical Use Contraceptive Implant more than 99% effective. They work for 3 years but can be taken out earlier. Fewer than 1 in 100 women using the implant will get pregnant in a year. Intrauterine System (IUS) more than 99% effective. An IUS normally works for 3 to 5 years depending on the type but can be taken out earlier. Fewer than 1 in 100 women will get pregnant over 3 to 5 years when using an IUS. Intrauterine Device (IUD) more than 99% effective. An IUD can stay in place for 5 or 10 years depending on the type but can be taken out at any time. Fewer than 1 in 100 women will get pregnant in a year depending on the type of IUD. Older types are less effective.

Choice of birth control is a deeply personal decision that involves understanding the limitations and potential risks of each method. While birth control pills offer a high level of effectiveness with perfect use, they are not immune to human error. Exploring the broader spectrum of birth control options, such as implants, IUS, and IUDs, can help ensure that you choose the method that best suits your lifestyle and needs.