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The female body goes through several phases during each menstrual cycle, although the specific length of each phase varies from woman to woman. The cycle begins with the menstrual period. Some women may experience a few days after the period during which they are not bleeding and are not able to become pregnant. In the middle of the cycle, there are about 6 potentially fertile days leading up to and immediately after ovulation. Once ovulation has occurred, pregnancy is very unlikely to result after intercourse later in the cycle. When coupled with the understanding that sperm from the male body live for a maximum of about 5 days, we can determine when in the cycle pregnancy is most likely to occur.
Women can learn to identify signs that tell them which phase they are in, including waking (or “basal”) body temperature, appearance of cervical mucus seen when wiping, and hormones detected in the urine. Many women are already keeping track of the pattern of when their periods occur on a calendar. Birth control that uses these signs is called “Fertility Awareness Based Methods” (FABMs). When trying to avoid pregnancy with FABMs, women avoid unprotected intercourse during potentially fertile times in the cycle. The converse is also true: women can use FABMs to identify fertile times in the cycle if they wish to conceive.
For the first time, the FDA recently approved two apps for contraception: Natural Cycles with 93-98% effectiveness and Clue with 92-97% effectiveness. Natural Cycles uses daily waking body temperature measurements and knowledge about a woman’s recent menstrual cycle to show when unprotected intercourse might lead to pregnancy. It is available now for use by women in the US. Clue uses an algorithm based on recent menstrual cycles to determine which days in the cycle might be fertile days. This feature is expected to become available in the near future. There are many other cycle tracking apps like Kindara and Flo, but these have not been approved specifically for use as contraception.
In addition to these apps, there are several ways that women can learn to identify these signs during the menstrual cycle for themselves. The Marquette Method, which uses changes in cervical mucus and monitoring of hormones found in urine, is one of the most effective FABMs. It has been shown to be 98% effective when used correctly. With this method, women check the consistency of their cervical mucus each day. They also use a ClearBlue Fertility Monitor and test strips to test levels of estrogen and LH (luteinizing hormone) in their urine on specific days. They chart these signs and avoid intercourse when fertility is high if they are avoiding pregnancy. Marquette Method is also helpful to couples trying to conceive. It is necessary to work with a teacher like me who is specially trained to teach women how to follow the Marquette Method.
FABMs can be used in some forms by people of any religion and regardless of any allergies or dietary restrictions. They are not right for everyone, though, particularly if unintended pregnancy might be dangerous for you or if you have trouble following routines. If you are interested in learning more, please reach out to your healthcare provider.
For factual information on contraception, visit the CDC's website or Bedsider, a website dedicated to contraception information.