Missed Birth Control Pill: Pregnancy Risk and Effectiveness Explained

The likelihood of pregnancy after missing a dose of birth control pills?

Hello doctor, I have been taking the 21-day oral contraceptive pill for seven months.
However, on the night of January 12th, I had sexual intercourse and ejaculation occurred.
I took the contraceptive pill that day, but I forgot to take it on the night of January 13th.
When I realized I missed it on the night of January 14th (approximately 24 hours later), I took two pills at that time, and I was already in the third week of this month's pill pack (the 15th pill).
I continued taking the pills normally afterward.
My questions are: 1.
Given that I missed one pill, what is the likelihood of pregnancy from the intercourse on January 12th? 2.
Will the effectiveness of contraception decrease during the subsequent period?

Meimei, 20~29 year old female. Ask Date: 2020/01/18

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, it should be safe, so please rest assured.
Wishing you good health.

Reply Date: 2020/01/18

More Info

When it comes to missed birth control pills and the associated risks of pregnancy, it is essential to understand how hormonal contraceptives work and the implications of missing a dose. Birth control pills, particularly combination pills that contain both estrogen and progestin, are designed to prevent ovulation, thicken cervical mucus, and thin the uterine lining. When taken consistently and correctly, they are highly effective in preventing pregnancy, with a failure rate of less than 1% with perfect use.

In your case, you mentioned that you have been taking the pill regularly for seven months but missed a dose on January 13 after having unprotected intercourse on January 12. Since you took the missed pill as soon as you remembered (within 24 hours), you have mitigated some of the risk associated with missing a dose. However, it is important to note that the effectiveness of the pill can be compromised if a dose is missed, especially if it occurs during the third week of the pill cycle.

1. Pregnancy Risk After Missing a Pill: The risk of pregnancy increases if a pill is missed, particularly if it is missed during the last week of the active pills. Since you had unprotected intercourse on January 12 and missed the pill on January 13, the risk of pregnancy is present, but taking two pills on January 14 helps to restore some of the contraceptive effectiveness. The general recommendation is that if you miss a pill, you should take it as soon as you remember and continue taking the remaining pills as scheduled. If you miss a pill during the third week, it is advised to skip the placebo week and start a new pack immediately to maintain contraceptive protection.

2. Effectiveness After Missing a Pill: After missing a pill and taking it as soon as you remembered, your contraceptive effectiveness is likely to remain high, especially since you have resumed taking the pills regularly afterward. However, it is crucial to use backup contraception, such as condoms, for at least seven days after missing a pill to ensure protection against pregnancy. If you experience any symptoms of pregnancy, such as a missed period, nausea, or breast tenderness, it is advisable to take a pregnancy test.

In summary, while missing a birth control pill does increase the risk of pregnancy, taking the missed pill promptly can help mitigate that risk. It is essential to follow the guidelines provided with your specific birth control method and consult with your healthcare provider for personalized advice. If you have further concerns about your contraceptive method or potential pregnancy, discussing these with your healthcare provider can provide clarity and peace of mind.

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