In Short: FAM works by determining the date limits for periods of fertility and infertility. Setting the start date of one phase automatically determines the end date of the previous phase. The start date for Phase 1 low fertility is set based upon menstruation. The start of Phase 2 fertility is set based upon the presence of cervical fluid or by using a formula based upon historical cycle length. The start of Phase 3 infertility is set based upon temperature changes alone or a combination of temperature and cervical fluid changes.Obviously, there is no real need to set the end date for any particular phase, as it is automatically set when you set the start date for the next phase. FAM uses the signs of menstruation, cervical fluid, and temperature to set these start dates.Determining the Start of Phase 1 Low FertilitySetting the start date of Phase 1 is easy -- it's the first day of menstruation. Phase 1 is said to be infertile, but as you get near the end of it, it becomes slightly more fertile. This is due to its closeness to ovulation and the fact that it is sexual relations before ovulation that most frequently result in pregnancy. The ovum only survives about 24 hours on its own, so sexual relations that take place 24 hours after ovulation won't normally result in conception. However, sexual relations as many as 5 days before ovulation may result in conception.
For this reason, it is very important to set the start of Phase 2 fertility accurately.Determining the Start of Phase 2 FertilityIf you recall from our discussion of the clues to fertility, cervical fluid is a positive sign of fertility. This means that the start of the fertile period, Phase 2, is set on the first day that cervical fluid with more fertile qualities appears. Originally, FAM dictated that when any cervical fluid appears, you are to be considered fertile. However, "sticky" cervical fluid and vaginal sensations are not very fertile, so this rule has been adjusted for pregnancy achievers to have fertility begin when "creamy" cervical fluid or "wet" vaginal sensations appear. This is because creamy and eggwhite-quality cervical fluid allow sperm to live up to 5 days, which means that ovulation doesn't have to occur just after sexual relations for a woman to conceive a child. On the other hand, without cervical fluid, sexual relations do not normally result in conception (we say "normally" because even though it's highly unlikely, anything is possible!) Therefore, FAM (for pregnancy achievers) treats the start of fertility, Phase 2, as being the first day more fertile quality cervical fluid is present.
What if you're not observing your cervical fluid and have decided to use menstruation and basal body temperature as your only signs? Or what if you normally do use cervical fluid but for whatever reason, you fail to do so in the current cycle? FAM will use a day-counting algorithm to begin the start of the fertile phase in such a situation. The TCOYF Fertility Advisor will alert you to this fact.A Note about Cervical Fluid Changes as Ovulation ApproachesCervical fluid first appears during Phase 2 and changes in quantity, color and consistency as ovulation approaches. The less fertile type of cervical fluid is typically sticky or crumbly with it becoming creamy and opaque as it becomes more fertile. The most fertile type is like raw eggwhite (wet, stretchy, slippery, and clear)
Armed with this knowledge, pregnancy achievers can be fairly certain when their chances for conception are highest. Just after ovulation, the hormone progesterone is released and estrogen levels drop, causing cervical fluid to begin "drying up" -- it goes from the more fertile to a less fertile type. The first day of this change, fertility and conception chances are still high. Within a day, the conception chances drop considerably, so sexual relations are advised through this transitional period to achieve pregnancy.Determining the Start of Phase 3 / Post-ovulation InfertilityThe start date for Phase 3 infertility can be set based on temperature changes alone, or better yet, based on a combination of temperature changes and changes in cervical fluid characteristics.
FAM requires there to be a significant upward shift in basal body temperatures for at least three consecutive days over the previous six days. All temperatures should be undisturbed by late rising, sickness, physical exertion, etc. This again points to the value of taking your temperature the FIRST thing in the morning, as there is less chance that these readings will be disturbed.
What determines whether a rise in temperature is significant? FAM uses a number of rules for determining whether this condition has been met. First, a coverline is drawn 0.1° F (0.05° C) above the highest of the six pre-shift temperatures. Once 3 or more temperatures are above the coverline, a thermal shift is said to have taken place.
While it goes beyond the scope of this primer to explain it in detail (Taking Charge of Your Fertility covers it in great depth), temperature rises are categorized in the following manner:* Standard Thermal Shift: Three successive days with temperatures above the coverline.* Slow-rise Thermal Shift: The first temperature in the shift is at the coverline; the remaining temperatures are above the coverline. Requires four successive days with temperatures above the coverline to identify ovulation using this pattern.* Fall-back Thermal Shift: The first temperature is above the coverline, the second dips back to or below the coverline, followed by two or three temperatures above the coverline. The first temperature might also be eliminated using the Rule of Thumb, which would then make this shift mimic the Standard Thermal Shift Because of this, a fall-back pattern requires corroboration by a dry-up of your cervical fluid.
Once in Phase 3, you are infertile through Phase 1, so you may elect to stop observing your temperature and cervical fluid symptoms until menstruation starts. Both temperature and cervical fluid observations should be resumed in Phase 1 right after days of heavy menstrual flow have subsided. A Final Note on Cervical FluidSome may find the idea of observing their cervical fluid sign to be, well, less than exciting. It does, however, provide a wealth of information about fertility and has a MAJOR advantage for those that use it: It more accurately identifies the period of Phase 2 fertility than cycle history or temperature alone. For those trying to achieve pregnancy, this is invaluable because changes in it represent positive signs of increasing fertility.