Fertility Awareness Birth Control - BBT

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Written by Allen Lawrence, M.D.

What is the Fertility Awareness Birth Control?

Fertility awareness birth control or often referred to as Basal Body Temperature Method, or even more simply as BBT method, works on the basis of understanding how your reproductive system works by observing and charting your body temperature. If you take your temperature immediately upon awakening, which is generally referred to as your basal body temperature you can within a short time determine when you ovulate. By correlating how you feel, breast tenderness, abdominal discomfort you can quickly begin to recognize when you are about to ovulate and when you actually ovulate (release and egg, and hence able to become pregnant), your so-called signs of fertility. These signs determine when you ovulate and hence when you can become pregnant. Since most women are actually only fertile during one-quarter of their menstrual cycle, knowing when this period occurs will allow them to have unrestricted sex during the other three-quarters of the month. This is also a great way to learn more about your body.

What is the Basal Body Temperature (BBT) Method?

The basal body temperature method also referred to as the calendar rhythm method or simply rhythm method) is possibly the oldest and most widely practiced of birth control. Since every woman is different and your ovulatory patter may vary from other women, you must establish what your ovulatory pattern is before you can use this method.

To help you determine when you ovulate we can share some basic information. 1) Most women ovulate (release an egg from the ovary) at about 14 days before their next menstrual cycle. Ovulation generally occurs between 2 days before or after the actual 14^th and 16^th day of her cycle and 14 days before her next menstrual period. When a woman has 28 daycycle (using the first day of one cycle to the first day of the next cycle to determine the length of the woman's menstrual cycle) then ovulation would generally occur between the 12 and 16 day, usually on the 14th day.

On the other hand, if a woman has a longer cycle say 35 days, ovulation would occur still14 days before the next menstrual period or day 19 to day 21 of her cycle. If a woman's cycle is regularly shorter say 24 days, then ovulation would generally occur between the 9^th and 12^th day of her cycle. This is only meaningful, however, if your menstrual periods are regular and always consistent in the number of days between one cycle or another. The actual time you bleed is not important, only the length of your cycle is important.

Another factor in determining your safe period during which you can safely have sex and not worry about pregnancy is that an egg is viable for about 1 day, and sperm can live for 2-3 days.

Now let us help you to put this information to work for you:

There are _________ (legnth of your menstrual cycle fore example 24, 28 30 or 35) days between the first day of one period and the first day of the next menstrual period.

Now subtract - 14 days from this number of days: Legnth of menstrual cycle - 14 = . For example: 27 - 14 = 13. This equals the number of days before your next menstural period you are most likely to ovulate. For example: If themonth before last the first day of your menstural period started on January 1 and your next menstrual period started on January 27, hence you had a 27 day long cycle, you will likely be ovulating 13 days from January 27.

This is how you can find the approximate day that you would be ovulating, if your menstrual periods are regular say ever 27 days. Of course the day would change as the number of days of your menstrual cycle change, but it will most likely always stay 24 days before the first day of the next menstural period.

Since, as was stated above, the egg can live two to three days we should add one to two more dasy to the days after ovulation and since sperm can live 2 to 3 days we should add 3 days to the before ovulation number.

Now then subtract 5 from this number and then add 3 to this number.

This should give you a range of two days before the day of ovulation and two days after ovulation. This is the period during which you should not have unprotected sex.

Therefore if you had a perfect 28 day cycle and ovulated approximately on the 14^th day you would then subtract 5 from 14 = 9 and then add 3 to 14 and = 17. Hence the unsafe days would be days 9 through 17. During this period you can have sex, but you should use foam and condoms, diaphragm or at minimum a spermicidal product or some other form of contraception if you want to prevent getting pregnant. (See Figure 1)

Figure 1.

How Do I Chart My Basal Body Temperature?

Make a chart like the one pictured below, but without the example line. Keep a daily calendar record of your temperature using a regular thermometer under the tongue for 3 minutes or purchase a Basal Body Thermometer and kit at your local drug store. Take your temperature immediately upon waking up in the morning even before you get out of bed, brush your teeth or go to the rest room. On the same record, chart your menstrual cycle, beginning with day 1 as the first day of your period. If possible, chart your temperature pattern for a few months before relying on it.

When Can I Have Sex Using this Method?

If you don't want to get pregnant, it is safe to have unprotected sex after your temperature rises above your normal temperature for 3 days in a row. This indicates that ovulation has occurred and the egg has already passed.

If you want to get pregnant, your most fertile days are those just before your temperature begins to rise during ovulation. It's generally difficult to predict this time, so practice the temperature method until you know your pattern.

Advantages:

The basal body charting method is free.

This method does not involve taking pills.

No foreign object is put into your body.

There are no side effects.

You and your partner rely on each other for mutual support and commitment to make this method work.

If used correctly every time, the failure rate of this method is 1%-9%.

Disadvantages:

The basal body temperature method does not protect you from HIV/AIDS or other sexually transmitted infections. This method is not a good choice if:

Your periods don't come at a regular time each month,

Your temperature pattern is different each month,

You just stopped taking birth control pills,

You just started having periods,

You are close to menopause,

You can't keep a calendar chart, or

You don't like going without sex for at least 2 weeks.

Where Can I Learn More about Basal Body Temperature Charting and Other Birth Control Methods?

Your doctor is the best place to start. There are also several good books you could look up specific information or read:

Taking Charge of Your Fertility: The Definitive Guide to Natural Birth Control and Pregnancy Achievement by Toni Weschler

Fertility Awareness Handbook by Barbara Kass-Anese.

What If I'm Using the BBT Method and I Have Sex During an Unsafe Time?

You then have 72 hours AFTER any episode of unprotected sex during which you can take emergency contraceptive pills to avoid becoming pregnant. For up to 7 days AFTER unprotected sex, you can have an IUD put in. However, not all medical doctors know about emergency contraception it is wise to discuss this possibility with your doctor to be sure that he or she either knows what to do or can refer you to a doctor who does.

Directions to Use BBT Chart

Take your basal body temperature daily through 4 cycles (four months).

Place a dot under the day of the month. Place the dot at the temperature reading with even numbers for example: 99.4 or 98.6 or 97.8 in the middle of the box.

Figure 2.

When the temperature number is odd, say 99.5 or 98.7 or 97.3, place the dot on the line between the even numbers. (See Figure 2)

Once all of the dots are in place for the month, connect the dots. (See Figure 2)

Place a dot under the days you have unprotected sex and days where you use a birth control method. Mark where you have any symptoms before ovulation or before your menstrual period. There is room to add other symptoms not already listed.