Pregnancy Chances After Contraceptive Use: Your Questions Answered

Probability of Pregnancy

Hello Doctor, I would like to ask: I have been taking the oral contraceptive pill (Yaz) from January until now in August.
My last menstrual period was from July 13 to July 30, and I experienced light bleeding after the fifth day.
On August 5, I had sexual intercourse with my boyfriend, and he accidentally ejaculated inside me.
The next day, on August 6, I purchased emergency contraception to prevent pregnancy.
My period was originally due on August 10, but as of now, August 12, according to my app, my period is already two days late.
Since I have been taking the oral contraceptive pill, my menstrual cycle has been consistently 28 days.
What is the likelihood of pregnancy in this situation? What could be causing the delay in my period? Thank you, Doctor.

Liao Xiaojie, 20~29 year old female. Ask Date: 2021/08/12

Dr. Wu Xianghui reply Obstetrics and Gynecology

1.
For pregnancy concerns, please perform a home pregnancy test or visit a gynecologist for examination and evaluation four weeks after your most recent sexual intercourse.
2.
The menstrual cycle can be influenced by various psychological and physiological factors.
If your period is more than two months late, it is recommended to consult a gynecologist for examination and evaluation.

Reply Date: 2021/08/12

More Info

When it comes to understanding the chances of pregnancy after contraceptive use, it's important to consider several factors, including the effectiveness of the contraceptive methods used, the timing of intercourse, and any potential disruptions in your menstrual cycle.

In your case, you have been consistently taking a daily contraceptive pill (Yasmin) from January until August. Birth control pills are generally very effective when taken correctly, with a failure rate of less than 1% per year. However, factors such as missed doses, gastrointestinal disturbances (like vomiting or diarrhea), or interactions with other medications can reduce their effectiveness.
You mentioned that you experienced some light bleeding after your last menstrual period, which can sometimes occur due to hormonal fluctuations caused by the pill. This is known as breakthrough bleeding and is not uncommon among women using hormonal contraceptives. The fact that you had unprotected intercourse on August 5, followed by taking emergency contraception (Plan B) the next day, further complicates the situation. Emergency contraceptive pills are designed to prevent ovulation and are most effective when taken as soon as possible after unprotected intercourse. They can be up to 89% effective if taken within 72 hours, but their effectiveness decreases the longer you wait.

Now, regarding your missed period: it is possible that the emergency contraceptive pill could cause a delay in your menstrual cycle. Hormonal fluctuations from both the regular contraceptive pill and the emergency contraceptive can lead to changes in your cycle, including delayed menstruation. Stress and anxiety about the possibility of pregnancy can also affect your menstrual cycle, leading to a missed or late period.

Given that your period was expected on August 10 and is now two days late, it is advisable to take a home pregnancy test for a more definitive answer. These tests are designed to detect the hormone hCG, which is produced after a fertilized egg implants in the uterus. If the test is positive, it would indicate that you are pregnant. If it is negative and your period still does not arrive, you may want to consult with your healthcare provider for further evaluation.

In summary, while the chances of pregnancy are relatively low due to your consistent use of the contraceptive pill and the timely use of emergency contraception, it is not impossible. The delay in your period could be attributed to hormonal changes from the contraceptives or stress. Taking a pregnancy test will provide clarity on your situation. If you have further concerns or if your period does not arrive soon, it would be wise to seek medical advice for additional support and guidance.

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