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Natural Family Planning: Ovulation Methodof NFP

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The Ovulation Method involves the daily monitoring of a woman's cervical mucus. By tracking the changes in the presence and characteristics of her cervical mucus, a woman can reliably tell when she is and is not fertile.

Several variances of the Ovulation Method are currently in use in the United States and being taught world-wide: the Billings Ovulation Method, Creighton Model Fertility Care System and the Family of the Americas Foundation Method.


The Billings Method

The Billings Ovulation Method (BOM) was first introduced in the 1960s, and relies on the woman's daily self-examination and charting to detect changes in her cervical-mucus Characteristics throughout her menstrual cycle. These changes are entered daily on an Ovulation chart or NFP chart.

The Billings Method is successfully taught around the world and is endorsed by the World Health Organization.


  • This method is over 99% effective when used correctly (Click link to see large-scale trial results)
  • It involves no tools except for a chart, which could be improvised in needed
  • It is approved by the Catholic Church as an acceptable form of pregnancy prevention
  • There are NO side effects
  • It can also be used to achieve pregnancy


  • Because she is observing only one fertility sign, this method invloves abstaining from intercouse during more days than other methods of NFP.
  • There is some risk of human error on the part of the woman detecting the presence and quality of her cervical mucus

What are the Common Symbols Used to Chart Mucus?

C = clear; a more-fertile type

CL = cloudy; generally a more-fertile type

D = dryness; non-fertile

M = less-fertile mucus but you cannot describe it more fully

O = opaque; generally a less-fertile type

P = Peak Day

S = stretchy; a more-fertile type

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SL = slipperiness; a more-fertile type

SR = seminal residue; this can look like mucus.

T = tacky; a less-fertile type

W = wetness; a more-fertile type

How does the Billings Method Work?

After her menstrual period, a woman experiences a series of "dry" days, that is she does not detect cervical mucus of any kind. As this is an infertile period, (called phase 1: "Pre-ovulation Infertile Period" of the fertility cycle) a woman looking to avoid pregnancy may safely have intercourse in the evening of these days.

However, she should avoid having intercourse in the morning during Phase 1 or on consecutive days, as semenal residue can mask the appearance of mucus. Of course, should a couple have serious reasons to avoid pregnancy, or until the woman is confident in her ability to detect the presence of mucus, it would be wise to avoid intercourse during this phase.

After a variable number of "dry" days, a woman should start to notice an increasing amount of mucus. At first, this mucus is tacky, but as ovulation gets closer, it becomes more watery and slippery, peaking at or just before ovulation.

A couple looking to prevent pregnancy who are using only the Billings Method should avoid intercourse from the day the woman notices cervical mucus of any kind, until the 4th day after her mucus level has reached its peak.

2-Day Method of Fertility Awareness

The two-day method of fertility awareness is very similar to the Billing's Method, except that a woman considers herself fertile only if mucus is present on the current or previous day. Breastfeeding woman, women in the pre-fertile time after pregnancy and pre-menopausal women should not use this method.

The 2-Day Method is over 99.4% effective when used correctly; however when user error is included in this rate, (user error includes taking risks and not charting correctly) the effectiveness rate drops to about 80%. This method should only be used by experienced NFP users who are confident in their ability to identify their fertile period.

Learn More about NFP

  • Sympto-Thermal Method of NFP
    The sympto-thermal method of NFP is the most involved but also the most reliable. Learn about this safe and reliable way to avoid or achieve pregnancy.
  • Natural Family Planning, NFP
    Natural Family Planning (NFP) is a way of following God's Plan for achieving and/or avoiding pregnancy. It consists of ways to achieve or to avoid pregnancy using the physical and moral means that God has built into human nature.
  • Introduction to Natural Family Planning
    Natural Family Planning is an umbrella term describing several types of family planning that teaches women to identify their fertile days each month. Couples then use this information to help them conceive a...

Learn NFP at Home

Calendar-Based Method

The Calendar Method (or Standard Days Method) is a variation on the calendar-rhythm method. It is strictly meant for women with regular cycle between 26 and 32 days ONLY. Women with irregular cycles and couple with serious reasons to prevent pregnancy should use a different NFP method.

With this method, a woman simply tracks which day in her menstrual cycle she is on and avoids intercourse during days 8-19 if the couple wishes to avoid pregnancy. It is the easiest method to learn and does not require the woman to be literate; it is currently being tested in many third-world countries.

© 2011 Sarah


ChrisLingCheng on September 08, 2013:

One thing I learned after reading, calendar method is out. I have a 39/40-day cycle so we'd have to put an X mark on that one. We'll read more about the other two.

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