the Risks of Irregular Birth Control Pill Usage

Taking birth control pills at irregular times?

Hello Doctor, my girlfriend started taking the oral contraceptive pill "Wenburen 21+7" a while ago.
She began taking it on the second day of her menstrual period, which was on November 26.
We only engaged in sexual intercourse seven days after she started taking the pill, and we did not use condoms during subsequent sexual encounters.
She has now completed all 21 pills.
Although my girlfriend takes the medication daily, the timing is not consistent (for example, she took it at 8 AM on December 1, then at 9 PM on December 2, and at 3 PM on December 3).
Sometimes the intervals between doses exceed 36 hours.
I would like to ask the doctor what the chances are of my girlfriend becoming pregnant.
Additionally, if she does have her period this time, when can we expect it to occur? Thank you, Doctor.

YP, 20~29 year old female. Ask Date: 2022/12/18

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello,
Combination oral contraceptives must be taken at the same time every day to achieve a 99% effectiveness in preventing pregnancy.
If you miss a dose for more than 24 hours, you should stop taking the current pack of contraceptives and refrain from taking them for seven days (including the days you missed).
After that, you can continue with the next cycle.
If you miss a pill and do not experience expected withdrawal bleeding during the placebo week, you should suspect the possibility of pregnancy.
It is best to take the pills at the same time every day for a continuous period of 21 days.
After taking all 21 active pills, menstruation will occur during the seven days of placebo pills.

Thank you! Wishing you peace and health.

Dr.
Zhang

Reply Date: 2022/12/18

More Info

When it comes to the use of birth control pills, consistency and timing are crucial for their effectiveness. Your girlfriend is using a combined oral contraceptive pill (the "21+7" regimen), which typically involves taking 21 active pills followed by a 7-day break during which she would have her menstrual period. The effectiveness of these pills can be significantly compromised if they are not taken at the same time each day or if doses are missed.

In your case, since your girlfriend has been taking the pills inconsistently—sometimes taking them at different times of the day and occasionally exceeding the 36-hour window between doses—this could increase the risk of unintended pregnancy. The general recommendation is that if a pill is taken more than 24 hours late, it may not provide adequate contraceptive protection, especially if unprotected intercourse occurs during that time.

The risk of pregnancy is higher if pills are missed or taken irregularly, particularly during the first month of starting the pill. Since your girlfriend started taking the pills on the second day of her menstrual cycle and had unprotected sex after the seventh day, she may have been somewhat protected by that point, but the irregularity in her pill-taking could still pose a risk.
As for when she might expect her next period, if she has taken all 21 active pills correctly, she should expect her withdrawal bleed (which mimics a menstrual period) during the 7-day break after finishing the active pills. If she has taken the pills inconsistently, it may be difficult to predict exactly when her period will come, as irregular pill usage can lead to irregular bleeding patterns. If she does not get her period during the break, it would be advisable for her to take a pregnancy test to rule out pregnancy.

In summary, the irregular usage of birth control pills can lead to an increased risk of pregnancy, especially if pills are taken late or missed. If your girlfriend has concerns about her risk of pregnancy or her menstrual cycle, it would be wise for her to consult with a healthcare provider. They can provide personalized advice and may suggest alternative contraceptive methods if irregular pill-taking continues to be an issue.

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