#fabm

The Method Types:

There are three main methods of modern FABM: the Creighton Model, the Marquette Method, and the Sympto-Thermal method. There is some overlap, but the main difference is what biological signs of ovulation the method tracks.

Creighton (and its predecessor, Billings) traditionally tracks just a woman's cervical mucus. Marquette utilizes daily urine tests to track chemical estrogen levels. Sympto-Thermal combines mucus, temperature, and cervical position tracking. I use the latter, so I'll explain that in the most detail.

Context:

When a woman ovulates, the egg released is viable for fertilization for about 12-24 hours. This means conception is possible for up to a day after ovulation has occurred. However, sperm can survive within a woman for 3-5 days after ejaculation, so a woman can potentially conceive if she has sex up to five days before ovulation or one day after - or six days total of a "fertile window". FABM work by using one or more of the aforementioned biological markers to identify when ovulation will occur.

Cervical Mucus:

As a woman nears ovulation, her body will begin secreting discharge called "cervical mucus". The mucus is necessary in providing a hospitable environment for the sperm to survive. It often starts out kinda thick and white, but the closer she gets to ovulation, the clearer and stretchier is becomes, and she can track this change in consistency.

In both the Creighton and Sympto-Thermal methods, generally the first day a woman notices cervical mucus is considered the start of the potential fertile window; if she wishes to avoid pregnancy, she must abstain from sex from now until she identifies the end of the fertile window (generally when she's had three days of "drying up", i.e. little or no mucus, after previously noting fertile mucus in the same cycle).

Basal Body Temperature:

A woman's body temperature changes slightly depending on where she is in her cycle. If she tracks her daily temperature, she can identify when she ovulated based on temperature change. Temperature cannot predict ovulation, but it can accurately tell you when the fertile window is over.

To track accurately, the woman must take her temperature at around the same time every morning before starting her day (as getting up and moving around will cause the temperature to rise) using a thermometer that measures to the 1/100th degree. If she has a sudden temperature spike, especially if it coincides with one of the other fertility markers, it might indicate ovulation. To rule out flukes, she must wait until she has had three days of elevated temperature in a row. The cluster of elevated temperatures must be at least 0.4F higher than the previous six day's temperatures. If it falls short of that benchmark, the woman must wait an additional day before marking the end of her fertile window.

Example: I usually average 97.6-97.8F pre-ovulation. When I ovulate, my temperature in the morning spikes to around 98.2-98.4F and will remain at that level until a few hours before my period begins.

Cervix:

Ovulation causes the cervix to physically change in texture and position. A woman can insert a finger into her vagina to feel her cervix and record her daily observations to assists in identifying when she nears ovulation. As she gets closer, the cervix will move higher up the vagina and soften.

This sign can be tricky to track because it relies on feeling alone. Some women (like me) can't really tell much difference in their cervix. However, this biological sign can be useful in corroborating one of the other ovulation symptoms.

Estrogen and LH Testing:

The Marquette method can optionally adopt any of the other symptom tracking, but it's main methodology is tracking a woman's hormone levels using disposable test sticks. Estrogen and LH hormones will rise leading up to ovulation.

For this, a woman must use urinate on a test strip (similar concept to pregnancy tests) around the same time every morning, and then insert the sample into a digital fertility monitor. When a sufficient level of estrogen has been reached, the fertile window begins.

This method is especially popular with breastfeeding mothers who are avoiding pregnancy but unsure when their cycle may return.

Conclusion:

Again, this is just a basic overview, so there are a lot of little rules I didn't go into. But this should give you a basic idea of how the various FABM work.