The Four Rules
- First Five Days Rule
You are safe during the first five days of the menstrual cycle if you have had an obvious temperature shift about 12 to 16 days prior.
This applies to the first five days of the cycle. Any bleeding after should be considered fertile whether you bleed or not. Bleeding in that 5 day period is true menstruation, not spotting or abnormal bleeding.
This rule can only work if you have been charting your cervical fluid and temperature for awhile. You cannot rely on this rule if you are approaching menopausal age and if any of the signs of menopause are present[i]. This is due to the hormonal fluctuations that occur in Premenopause.
If your last 12 cycles were 25 days or shorter, you should then assume only 3 days are safe. This precaution is due to the fact that you could ovulate earlier. You would not be able to detect cervical fluid change due to bleeding.
- Dry day Rule
Before ovulation you are safe any evening of every dry day[ii].
Dryness[iii] is determined by periodic checks of cervical fluid throughout the day. There should be no wet or any kind of fluid.
It must not be “sticky” either. Although sticky fluids may not be conducive to fertility, err on the safe side. Many women cannot distinguish between the sticky fluid and the wet fertile cervical fluids. But if you have a couple “sticky” days and then return to dry, you are then considered safe on the dry days.
on the day after intercourse you chart that day with a question mark if semen or spermicide is present, these tend to mask cervical fluid. Because the fluids are masked that evening is considered fertile, since you cannot determine “wet” or “dry” cervical fluid. But if by the end of the day after intercourse you are dry and have been all day, you are safe.
Remember: sperm cannot survive with a dry cervix. The longest that the sperm stays alive is just a few hours. The sticky fluid of the cervix is just about as inhospitable as a dry cervix, so the risk is low.
- Temperature Shift Rule
You are safe the evening of the 3rd consecutive day your temperature is above the cover-line.
You are infertile starting at 6 p.m. the third consecutive night that your temperature is above the cover-line. If the temperature falls on or below the cover-line during that three day time frame, you must start your counting over until it is above the line again.
If you develop a fever due to illness, you cannot consider yourself safe until you have had and recorded three days consecutively of normal temperatures above the cover-line. If you have had no obvious thermal shift use a more conservative rule. This would mean you would consider yourself safe only until the evening of the third day you are above the line.
- Peak Day Rule
You are safe the evening of the 4th consecutive day after your peak day
Your peak day is the last day of “wetness”. On the chart mark “PK” in the peak day column. Subsequent days should be marked as “1”, “2”, “3”, etc., in that same row. You should record them only in the evening after having observed your cervical fluid.
You are considered safe on the 4th consecutive day following a “peak day”after 6 p.m. Draw a vertical line on the 3rd and 4th day to indicate your being safe from day four.
Putting it all together
- The peak day of cervical fluids typically occurs a couple of days before the temperature rises.
- Before ovulation, the cervical fluid is the critical fertility sign to observe
- But after ovulation , it is the temperature that is a critical sign.
- The rules that apply to ovulation will often work in harmony with each other, so the the 3rd evening of high temperatures will coincide with the 4th evening after the peak day.
- If there is a discrepancy between the two post-ovulatory rules, always wait until both signs indicate infertility.
- If it is critical that you avoid pregnancy, do not take the chance of unprotected sex!
[i] Hot flashes, vaginal dryness, etc.
[ii] After 6 p.m.
[iii] No fluids present, the slight moisture at the vaginal opening is not “wet” per se.