Many individuals using birth control pills wonder about the risk of pregnancy, particularly during the week they take inactive pills. Understanding the function of these pills and how hormonal contraception works is important for effective use and to address concerns about potential pregnancy.
The Purpose of Inactive Pills
The “white pills,” or inactive pills, found in some birth control packs are placebos. They do not contain hormones but help maintain the routine of taking a pill every day, preventing users from accidentally skipping days.
While taking these inactive pills, individuals typically experience a withdrawal bleed, which resembles a menstrual period. This bleeding occurs because the body reacts to the temporary drop in hormone levels by shedding the uterine lining. This bleed is not a true period, as ovulation is generally suppressed by the active hormones. Some pill brands may include vitamins or minerals in these inactive pills, but they do not contribute to pregnancy prevention.
How Combination Birth Control Works
Combination birth control pills contain synthetic versions of estrogen and progestin. These active hormones prevent pregnancy in three primary ways. First, they suppress the release of hormones that trigger ovulation, preventing the ovaries from releasing an egg.
Second, the hormones thicken cervical mucus, creating a barrier that makes it difficult for sperm to travel through the cervix and reach an egg. Third, they thin the lining of the uterus, making it less receptive to a fertilized egg. These combined actions provide a highly effective method of pregnancy prevention when active pills are taken consistently.
Circumstances Leading to Pregnancy Risk
While combination birth control pills are highly effective with correct use, certain situations can compromise their effectiveness and increase pregnancy risk. Missing active pills, particularly those at the end or beginning of a pack, can extend the hormone-free interval and increase the chance of ovulation. Forgetting to start a new pack on time after the inactive pill week also creates a gap in hormonal protection. If multiple active pills are missed, or if a progestin-only pill (which has a shorter window of effectiveness) is missed, the risk of pregnancy rises.
Certain medications can also reduce the effectiveness of birth control pills. The antibiotic rifampin interferes with hormonal birth control by affecting hormone metabolism. Some anti-seizure medications, such as carbamazepine, phenytoin, and topiramate, as well as certain anti-HIV drugs like efavirenz, can also make birth control less effective. Additionally, the herbal supplement St. John’s Wort has been linked to reduced birth control efficacy. Most common antibiotics do not interfere with birth control.
Vomiting or severe diarrhea shortly after taking an active pill can also prevent the pill’s hormones from being fully absorbed into the body. If vomiting occurs within 3 to 4 hours of taking a pill, or if severe, watery diarrhea persists for more than 24 to 48 hours, the pill’s effectiveness may be reduced. If active pills were taken correctly before the inactive pill week, the protective effect generally extends through this period, provided the new pack is started on time.
Actions to Take and Prevention
If there is concern about potential pregnancy due to missed pills or other compromising circumstances, taking a pregnancy test is an important step. Home pregnancy tests detect the hormone hCG. For accurate results, take a test on the first day of a missed period, or at least 21 days after unprotected sexual activity if your period is irregular. If a test is negative but your period remains missed, take another test a few days later or consult a healthcare provider.
To maximize birth control effectiveness, take pills consistently at the same time each day. Keep a backup method of contraception, such as condoms, available. If one active combination pill is missed, take it as soon as remembered, even if it means taking two pills in one day. Backup contraception is not always needed in this case. However, if two or more active pills are missed, or if a progestin-only pill is missed, use backup contraception for at least seven days.
Consider emergency contraception if multiple pills are missed, or if pills are missed during the first week of a new pack, especially if unprotected sex occurred within the last five days. Always refer to the specific instructions provided with your birth control pill package for detailed guidance on missed pills, as recommendations vary by brand and type. Consulting a healthcare provider for personalized advice on managing missed pills, potential drug interactions, or any concerns about birth control effectiveness is always recommended.