Natural Family Planning
-written by Monica Byrne, CNM

There are days when a healthy woman is fertile, days when she is infertile, and some days when fertility is unlikely, but possible.  Understanding several basic concepts can help a couple to plan or prevent a pregnancy. 

The monthly pattern that occurs regularly in most women is called the menstrual cycle. Every cycle is divided into two parts — before ovulation and after ovulation.  The first part of the cycle, from the first day of menstruation to ovulation, may vary from 13 to 20 days in length. The length of the first part is not only different from one woman to another, but also can differ in some women from month to month.  The second part of the cycle, from ovulation to the first day of menstruation, is about the same length in all women. The egg is released consistently 14-to-16 days before the onset of menstruation, regardless of the length of a woman’s menstrual cycle.

The fertile period depends on the life span of sperm as much as it does on the life span of an egg. The egg lives for about a day. A man’s sperm can live inside a woman’s body for up to about five days.  So in total, a woman has a good chance of becoming pregnant from unprotected vaginal intercourse over the course of about seven days of her menstrual cycle — as long as five days before the release of an egg (ovulation), the day of ovulation, and the day after ovulation. Fertilization of a woman’s egg is more likely from intercourse before or during ovulation than from intercourse following ovulation.  She is less likely to become pregnant from unprotected intercourse in the day or two following ovulation, but it is possible.

Women who monitor their fertility to prevent pregnancy need to either choose to abstain from vaginal intercourse for at least seven days of each menstrual cycle or to use barrier methods such as condoms, diaphragms, or cervical caps during that time.  Although they are abstaining from vaginal intercourse, they may enjoy other forms of sexual activity.  Those women trying to conceive would want to have sex every other day during this fertile period.

The key to knowing when fertilization may occur is being able to estimate the time of ovulation. This must be done carefully because the timing of ovulation varies greatly from one woman to another and, for some women, from one month to the next.

Ways to Chart Your Fertility Pattern

Here are brief descriptions of three charting methods you can use to predict when you ovulate in order to plan or prevent pregnancy.  It is best to combine the temperature method, the cervical mucus method, and the calendar method. The combination of these methods is called the symptothermal method.

Temperature Method

Each morning take your temperature, as soon as you wake up, before getting out of bed, talking, eating, drinking, having sex, or smoking. Either insert the appropriate thermometer into your rectum or place it in your mouth for a full five minutes. Read the temperature to within 1/10 of a degree and record the reading.  For most women, 96-to-98° F taken orally is considered normal before ovulation and 97-to-99° F after. The changes you are watching for are small fractions — from 1/10 to 1/2 degree. So it's best to get a large-scale, easy-to-read thermometer that registers only from 96 to 100° F.  Chart your temperature for at least three months before relying on this method. 

A women’s body temperature is lower during the first part of the cycle. In most women it usually rises between 0.4°F and 0.8°F with ovulation and remains up during the second part until just before her next period. The temperature method is quite accurate in detecting when ovulation has occurred, but can't predict when it's about to happen.  After the temperature rise has lasted for at least three days, you can assume that your infertile days have begun. They will last until the temperature drop that usually comes just before the onset of your next menstrual period. For complete protection, consider all the days between the start of your period and the start of the fourth day after the next temperature rise as fertile days.

It is important to realize that your BBT can be influenced by other factors such as physical or emotional upsets, lack of sleep, illness, emotional distress, jet lag, disturbed sleep, smoking, drinking alcohol the night before, or using an electric blanket. 

Cervical Mucus Method

The cervical mucus method is based on another hormonal change that occurs during the menstrual cycle.  The cycle begins with menstruation. During menstruation, the flow disguises the mucus signs.  The menstrual period is usually followed by a few days when no mucus is present — these are “dry days.”  The dry days are nonfertile days.  As an egg starts to ripen, mucus increases in the vagina and appears at the vaginal opening. It is generally yellow or white, and it is cloudy and sticky, or tacky.  The greatest amount of cervical mucus usually occurs immediately before ovulation during the “slippery days.” The mucus takes on a clear and slippery quality that resembles raw egg whites. It also will stretch between your fingers.  Fertilization is most likely to occur during this phase.  You would abstain from vaginal intercourse or use a barrier contraceptive during this time to avoid pregnancy.  After about four days of “slippery days”, the mucus may become cloudy and tacky, and decrease in amount.  This is the return to nonfertile days.  The fewest pregnancies occur when intercourse takes place only on the dry days after ovulation. 

It's suggested that a woman chart her observation daily on a calendar. Mark the days of your menstrual period, the dry days, sticky days, and slippery days. It's best to avoid intercourse for at least one whole cycle when you start to use the mucus method for birth control.  This method is less reliable for women who produce very little mucus or if the woman uses douches, "feminine hygiene" products, or contraceptive foams, creams, jellies, film, or suppositories.

The Calendar Method The calendar method attempts to predict ovulation using a woman's menstrual history. This method is most effective if your cycles are the same length.  If your cycles vary from month to month, it will be more difficult to predict the day of ovulation.  In that case, you will have more potentially fertile days.  A written record is very important.  The day your bleeding starts is Day 1, mark this on your calendar. Continue to track the first days of your period for at least eight cycles; 12 is even better. Then you count the days in each cycle.   Sample Cycle Record First Day of Period Number of Days in Cycle First Day of Period Number of Days in Cycle Jan. 20   May 12 26 Feb. 18 29 June 9 28 Mar. 18 28 July 9 30 Apr. 16 29 Aug. 5 27 To find the first day you are likely to be fertile, check your record of previous months, find the shortest cycle, and subtract 18 from the total number of days. For example, if the shortest cycle is 26 days long, subtract 18 from 26, which is eight. Starting with the first day of your current cycle, count ahead eight days and draw an X through that date. That's the first day you're likely to be fertile and, therefore, the first day of abstinence or contraceptive use in order to avoid a pregnancy. To find the last day you are considered fertile, subtract 11 days from your longest cycle. For example, if your longest cycle is 30 days, then 30-11 is 19. Starting from the first day of your cycle, count 19 days and draw an X through that date also.  The days in between and including the dates with an X represents your fertile time.  Be sure to confirm this with other methods. If all of your cycles are shorter than 27 days, don't try to use the calendar method. Trying to add a few days of intercourse in the early part of your cycle can be risky when attempting to prevent an unplanned pregnancy.  Monitoring your temperature and cervical mucus may reduce miscalculations.  Pay attention to any sign that says you may be fertile. Sympothermal Method Using all three methods — temperature, cervical mucus, and calendar — is called the symptothermal method. The symptothermal method allows a woman to be more accurate in predicting her unfertile days than if she uses any one of the methods alone. When using these methods together, the signs of one can serve to confirm those of the other.  Combining methods also permits sexual relations during the early dry days of the mucus method, and shortens the period of abstinence necessary for complete protection when using the temperature method alone. Effectiveness for Contraception Of 100 couples who use any of these methods for one year, 20 women will become pregnant with typical use. The failure rate is higher for single women. Combining the various methods with consistent use and having no unprotected vaginal intercourse during the fertile phase can give better results.  These methods do work better for women whose cycles are always the same length.  Women who are breast-feeding or approaching menopause have more difficultly charting their fertility.  If you are taking pills or any other hormonal method, you'll have to stop taking it and use another method of contraception that has no hormones, such as a barrier method (condoms, female condoms, diaphragms, cervical caps), while learning to chart your fertility. Hormonal contraception alters the natural menstruation and fertility cycle. Natural family planning can work for you if you have the self-discipline to check and chart your fertility signs and, if you are trying to avoid a pregnancy, don’t mind abstaining or using withdrawal or barrier methods for the first part of your cycle.  Test kits to predict ovulation are also available over-the-counter for home use. They can be very useful for planning pregnancies but are not reliable for purposes of birth control. They help determine when ovulation is about to happen, but with only a one to three day notice.  Because sperm can live in the fallopian tubes for five to seven days, pregnancy can result from unprotected vaginal intercourse that occurs prior to three days before ovulation.

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