Birth Control Pills: Effects on Menstrual Flow and Efficacy

Effectiveness of Birth Control Pills

Hello, doctor.
My girlfriend has been taking Yaz birth control pills (24+4) for about six months.
After starting the pills, her menstrual flow decreased, but after finishing the last pack, she mentioned that it has decreased even more.
On the third day, a 10cc tampon was not saturated at all.
Should she consider taking a break from the medication? Also, on Monday (February 28), we had intercourse with ejaculation when her period had just started a little.
She was supposed to start the next pack on Wednesday but forgot and took it a day late on Thursday.
On Friday at noon, she took an extra pill to catch up.
Will this affect the contraceptive effectiveness? Should we see a gynecologist for confirmation? The Yaz instructions say to start the next pack after a 4-day break, which is different from the 21-pill regimen that suggests starting again after five days of menstruation.
We are concerned that taking the next pack a day late might lead to pregnancy due to any sperm remaining.
Thank you for taking the time to respond.

Pi, 20~29 year old female. Ask Date: 2022/03/04

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, you should be in your safe period, so there is no risk of pregnancy.
Please rest assured, and I wish you good health.

Reply Date: 2022/03/04

More Info

Birth control pills, such as the one your girlfriend is taking (often referred to as a combination pill), can have various effects on menstrual flow and overall reproductive health. It's common for women to experience changes in their menstrual cycle when they start taking hormonal contraceptives. These changes can include lighter periods, irregular bleeding, or even missed periods altogether.
In your girlfriend's case, the reduction in menstrual flow after starting the pill is not unusual. Many women report lighter periods due to the hormonal effects of the pill, which can thin the uterine lining and reduce the amount of blood shed during menstruation. The fact that her flow has decreased further after the second pack may simply be a continuation of this effect. However, if she is experiencing very light periods or spotting that is concerning to her, it may be worth discussing with a healthcare provider to rule out any underlying issues.

Regarding the missed pill, it's important to follow the instructions provided with the medication. Generally, if a pill is missed, it should be taken as soon as remembered, and the subsequent pills should be taken at the regular time. In your case, since your girlfriend missed taking the pill on Wednesday and took it on Thursday instead, her contraceptive efficacy may be compromised, especially if she had unprotected intercourse during that time.
The effectiveness of birth control pills can be reduced if pills are missed, particularly if they are missed in the first week of a new pack. Since she had unprotected sex shortly after missing a dose, it would be prudent to consider emergency contraception if she is concerned about the possibility of pregnancy.
Additionally, it is important to note that sperm can survive in the female reproductive tract for up to five days, so if she had unprotected intercourse just before missing the pill, there is a potential risk of pregnancy. If she is worried about this, visiting a healthcare provider for a pregnancy test or further advice would be a good step.

In summary, while lighter menstrual flow is a common side effect of birth control pills, any significant changes or concerns should be discussed with a healthcare provider. Missing a pill can reduce the effectiveness of the contraceptive, and if there is any doubt about potential pregnancy, it is advisable to seek medical advice. Regular check-ups with a gynecologist can help monitor her reproductive health and address any concerns regarding her birth control method.

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