When to Start the Second Pack of Birth Control Pills After Missed Period?

If you have finished a 21-day course of birth control pills and your period has not started, you should begin taking the next pack of pills as scheduled, typically the day after you finish the last pill of the previous pack. If you have concerns about not getting your period, it is advisable to consult with a healthcare provider?

Hello, doctor.
From January 31 to February 20, I took my first pack of 21 oral contraceptive pills (Diane) primarily to regulate my menstrual cycle.
I took them at the same time every day without missing any doses, but it has been four days since I finished the pack and my period still hasn't arrived (I used condoms during sexual intercourse this month).
Today, I consulted with a gynecologist who provided me with a second pack, but the doctor advised me to start taking it on the fourth day after my period arrives.
However, I found online that many doctors and articles state that regardless of whether menstruation has started or not, one should continue taking the pills for seven days after finishing the first pack.
Could you please explain the difference between these two recommendations? If I start the second pack on the fourth day of my period, but it exceeds the seven-day window for taking the pills, will the contraceptive effectiveness be compromised?

Song Song, 20~29 year old female. Ask Date: 2022/02/24

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, please follow the doctor's instructions.
During this period, you will not become pregnant.
If your period does not arrive more than a week after finishing the last pack of birth control pills, it is advisable to return to the gynecologist for further evaluation.
Wishing you good health.

Reply Date: 2022/02/24

More Info

When it comes to starting the second pack of birth control pills after a missed period, there are several important considerations to keep in mind. Based on your situation, it seems you have been taking a 21-day birth control pill regimen (Diane) and have completed the first pack without experiencing a menstrual period during the expected time frame. You are now wondering whether to wait for your period to start before beginning the second pack or to start it regardless of whether your period has arrived.

Firstly, it is essential to understand how birth control pills work. The primary function of these pills is to prevent ovulation, thereby reducing the chances of pregnancy. When taken correctly, they can be over 99% effective. The typical regimen involves taking one pill daily for 21 days, followed by a 7-day break during which a withdrawal bleed (similar to a period) usually occurs. This withdrawal bleed is not a true menstrual period but rather a response to the sudden drop in hormones from stopping the pills.

In your case, since you have completed the first pack and have not experienced a withdrawal bleed, the recommendation from your healthcare provider to start the second pack after four days of your missed period is somewhat common. However, there is also a widely accepted guideline that suggests starting the next pack regardless of whether your period has arrived, as long as you are within the 7-day window after finishing the first pack. This approach helps maintain consistent hormone levels in your body and ensures continued contraceptive effectiveness.

If you choose to wait until your period arrives (or until the fourth day after it is due), you may be extending the time without hormonal coverage, which could potentially reduce the effectiveness of the birth control. If you exceed the 7-day break without starting the new pack, you may need to use additional contraceptive methods (like condoms) for the first seven days of the new pack to ensure you are adequately protected against pregnancy.

The difference between the two approaches primarily lies in the timing and the potential for reduced contraceptive effectiveness. Starting the second pack on the eighth day after completing the first pack (regardless of whether your period has come) is generally considered the best practice to maintain contraceptive efficacy. On the other hand, waiting for your period may lead to a gap in hormone intake, which could increase the risk of ovulation and, consequently, the risk of unintended pregnancy.

In summary, if you have completed your first pack and are within the 7-day break, it is advisable to start the second pack on the eighth day, regardless of whether your period has arrived. This will help maintain consistent hormone levels and ensure that you remain protected against pregnancy. If you have any concerns or if your situation changes, it is always best to consult with your healthcare provider for personalized advice.

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