I’ve written blogs about many options for contraception, but have failed to write about the oldest method, natural family planning (NFP).  The new term for this in the medical world is call fertility awareness-based (FAB) methods for pregnancy prevention.  Some women cannot or choose not to use birth control (pills, IUDs, etc) due to medical, religious, or cultural reasons; and thus, rely on FAB methods.  We will get into the details below, but the basic principle is to identify the fertile days of the menstrual cycle using a combination of cycle length and physical signs of ovulation—and then avoiding sex or using a barrier method on these days.  Now, a quick disclosure from me is warranted, I've never practiced FAB methods so all of this is based on my reading and prior knowledge of menstrual cycles and fertile windows.

 

Interestingly, only 1% of women in the United States use FAB/NFP contraception.  This is probably due to a combination of factors including a lack of information available for FAB, convenience of other available contraception, desire for other added benefits of other contraception (like lighter or more regular periods), and a concern about the efficacy.  Speaking of the latter, this varies based on which methods of FAB are used and whether a woman is a “typical” user or a “correct” user.  Typical use of FAB methods leads to up to a 24% pregnancy rate during the first year while correct use pregnancy rates vary from 0.4 to 5% depending on the method.  To compare this to the most commonly used contraception in the US, the typical use and correct use failure rates of birth control pills are 9% and <1% respectively. 

 

One of the mainstays of FAB/NFP methods is determination of the fertile window.  This is a six day time frame starting 5 days before ovulation and ending 24 hours after.  The critical thing here is being able to figure out the day of ovulation, which can be done with a combination of cycle length and physical manifestations of ovulation – cervical secretions and body temperature.


Cervical Secretions  (In this order cyclically)

  • Menses
  • No secretions for 3-4 days
  • Scant, cloudy, sticky secretions for 3-4 days
  • Abundant, clear, wet, stretchy secretions for 3-4 days immediately before, during, and after ovulation
  • No secretions for 11-14 days until the period starts over

Basal Body Temperature (BBT)

BBT, taken first thing in the morning before rising, increases by about 0.5 degrees starting 1-2 days after ovulation.  Thus this signals the end of the fertile window. 

 

Let’s look at some of the different FAB/NFP methods more closely.

Standard Days Method

This method is appropriate for women with regular, predictable periods that have a cycle length of 26-32 days (meaning from the first day of bleeding one cycle to the first day of bleeding the next cycle).  It basically assumes that if you are in this range regularly, then you will have a fertile window that starts as early as cycle day 8 and ends as late as cycle day 19 (remember cycle day 1 is the first day of menses).  During this 12 day window, you should use barrier methods or abstinence and then can have unprotected sex on the other days.  With perfect use the pregnancy rate in a year is <5%, but with typical use it is 12%.  There are many tool and phone apps that can help you track your cycle length and standard days.

 

Cervical Mucous

There are a few variations in using cervical mucous. I would suspect that very few medical providers will be able to counsel you well on this, as observing and evaluating your secretions is a learned skill individual to you.  The first method is sometimes referred to as the Billings or Creighton method.  It requires observing, recording, and interpreting cervical secretions based on the characteristics mentioned above.  Unprotected sex should be avoided during the following: 

- During menses, as the blood can obscure the presence of secretions if cycle length is on the shorter side.

- On preovulation days after intercourse, as the semen can confuse the secretion analysis.

- On all days with clear, wet, stretchy secretions

- Until 4 days past the presence of secretions

For most women using these guidelines, they avoid unprotected sex or abstain from sex 14-17 days per cycle.  With correct use there is a 3% failure rate, and with typical use a 23% failure rate.  A little easier method of using cervical mucous is called the “TwoDay” method, in which unprotected sex is avoided any time there are any secretions and for one day after the last time secretions were noted.  This is typically 10-14 days per cycle and has a failure rate of 3% and 14% with correct and typical use respectively.

 

Symptothermal Method

With this method, women use their cervical mucous to mark the beginnings of the fertile window and then the rise in BBT to mark the end.  They usually abstain or avoid unprotected sex for 13-17 days per cycle and there is a 2 and 13% failure rate with correct and typical use respectively. 

 

Methods Using Newer Technologies

There are several commercially available tools (microscopes, mini computers, etc.) available to help track this fertile window.  Many of them are not well studied and can be cost prohibitive.  The one I hear about most frequently from my patients is called the ClearBlue Easy fertility monitor. When used in conjunction with the calendar method, it can be quite effective.


If after reading this you are feeling the same way I feel writing this, you may be a little overwhelmed.  However, I have been told that these methods become easier as you get used to them and more comfortable with them.  As mentioned above it is really best to have regular, predictable periods to have these methods be reliable.  I did not feel it was in the scope of this post to get into the FAB/NFP methods during the postpartum and premenopause timeframes (when periods are much less predictable).  Online resources, such as the Couple to Couple League, are probably much better than this blog post for all aspects of NFP, and I encourage further research for those of you who are interested.