Missed Period After Emergency Contraceptive: Am I Pregnant?

Taking emergency contraception, if a pregnancy test shows negative but menstruation has not occurred, is it possible to be pregnant?

Hello Doctor: My menstrual cycle is usually around 34 days, and each period lasts about 5 days.
The last two menstrual periods were as follows: 12/31 to 01/04 and 02/03 to 02/07.
My next expected period should have been on 03/08.
I had sexual intercourse with my boyfriend on 03/22, which was estimated to be around ovulation.
Although he used a condom, it seemed to have slipped off, and I was worried about the possibility of pregnancy.
Therefore, on 03/25, I purchased an emergency contraceptive pill that is effective for 120 hours and took it.
After taking the pill, I did not experience any discomfort or bleeding.
However, my expected period on 03/08 did not arrive, so I bought a pregnancy test on 03/12, which showed one line.
Now, as of today, 03/16, my period still has not come, and I am very concerned about what might be happening.
I hope you can provide some answers, thank you, Doctor.

Bai Bai, 20~29 year old female. Ask Date: 2020/03/16

Dr. Huang Yuande reply Obstetrics and Gynecology

After taking the emergency contraceptive pill, menstruation will definitely be affected, which may result in either an earlier or delayed period.
It is recommended to wait one to two weeks before taking a pregnancy test.

Reply Date: 2020/03/16

More Info

When it comes to missed periods after taking emergency contraception, there are several factors to consider. Based on your description, it seems you have a regular menstrual cycle of approximately 34 days, with your last menstrual period starting on February 3rd and lasting until February 7th. Given this timeline, your next expected period would have been around March 8th.
You mentioned having unprotected intercourse on March 22nd, which is close to your estimated ovulation period. Although you used a condom, the concern about it slipping off is valid, as this could potentially lead to unintended pregnancy. To mitigate this risk, you took emergency contraception (Plan B) on March 25th, which is within the recommended time frame for such medications.

Emergency contraceptive pills (ECPs) are designed to prevent pregnancy after unprotected intercourse. They work primarily by delaying ovulation, preventing fertilization, or preventing a fertilized egg from implanting in the uterus. However, they are not 100% effective, and their efficacy can be influenced by factors such as the timing of administration relative to ovulation and your individual hormonal balance.

Now, regarding your missed period: it is not uncommon for menstrual cycles to be disrupted after taking emergency contraception. Many women experience changes in their cycle, including delayed periods, lighter or heavier bleeding, or even skipped periods altogether. The hormonal changes induced by the emergency contraceptive can affect your menstrual cycle, leading to a delay in your expected period.

You mentioned that you took a pregnancy test on March 12th, which returned a negative result. Given that this was just a few days after your expected period, it is possible that the test was taken too early to detect pregnancy, especially if you ovulated later than expected. Pregnancy tests are most accurate when taken after a missed period, and they can sometimes yield false negatives if taken too soon.

Since you are still experiencing a missed period as of March 16th, it would be advisable to wait a few more days and take another pregnancy test. If your period does not arrive within a week or two, or if you continue to have concerns, it would be wise to consult with a healthcare provider for further evaluation. They may recommend a blood test for pregnancy, which can detect lower levels of the hormone hCG (human chorionic gonadotropin) than urine tests.

In summary, while it is possible that you could be pregnant, the missed period could also be a result of the emergency contraception affecting your cycle. Monitoring your symptoms and possibly retesting in a few days will provide more clarity. If you have any further concerns or if your symptoms change, seeking medical advice is always a prudent step.

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