4.2.1  Periodic abstinence (fertility awareness) methods

During the menstrual cycle, the female hormones oestrogen and progesterone cause some observable effects and symptoms:

  • Oestrogen produces alterations in the cervical mucus, which changes from thick, opaque and sticky to thin, clear and slippery as ovulation approaches.
  • Progesterone produces a slight rise in basal body temperature (temperature at rest) after ovulation. Otherwise, the function of progesterone on the cervical mucus is just the opposite effect of oestrogen — it makes the cervical mucus thick, opaque and sticky.

Observation of these changes provides a basis for periodic abstinence methods. There are three common techniques used in periodic abstinence methods, namely:

  1. Rhythm (calendar) method
  2. Basal body temperature (BBT) method
  3. Cervical mucus (ovulation) method.

Calendar or rhythm method

This method is the most widely used of the periodic abstinence techniques. The calendar method is a calculation-based approach where previous menstrual cycles are used to predict the first and the last fertile day in future menstrual cycles. This method requires a good understanding of the fertile and infertile phases of the woman’s menstrual cycle. It is based on the regularity of the menstrual cycle and the fact that an ovum (egg) can only be fertilised within 24 hours of ovulation.

  • What do you know about the regular and irregular menstrual cycle of a woman?

  • A regular menstrual cycle is when monthly bleeding happens every month or 28 days.

    An irregular menstrual cycle is when monthly bleeding is variable from month to month, for example it can vary from 25 to 32 days in some women.

It is important for you to know that before relying on this method a woman needs to record the number of days in each of her menstrual cycles for a period of at least 6–8 months (remembering that the first day of menstrual bleeding is always counted as day 1). See Box 4.1 on how to advise women using the calendar method.

Box 4.1  Advice to women using the calendar method

For irregular cycles, identify the longest and the shortest cycles recorded over six to eight cycles.

  • Subtract 18 from the shortest cycle (gives the first day of the fertile phase).
  • Subtract 11 from the longest cycle (gives the last day of her fertile time).
  • Avoid sex, use a barrier method, or use withdrawal during the fertile phase calculated.

Example 1

  • A woman’s last six menstrual cycles were 28, 26, 29, 27, 29 and 27 days. Using this information, calculate and instruct her about how to use the calendar method to prevent pregnancy.

    • Her shortest cycle is 26 days.
    • Her longest cycle is 29 days.
    • First day of her fertile phase is 26 - 18 = 8.
    • Last day of her fertile phase is 29 - 11 = 18.

    Therefore, the fertile period of this client is between the 8th–18th days, so she should avoid sex during this period to prevent pregnancy.

    However, if the client’s menstrual cycle is regular and comes every 28 days or close to it, ovulation should occur about 14 days before the next period. For this reason, the woman should count backwards 14 days from her next period to calculate the day she will ovulate. Consequently, she should avoid sex from about seven days before that day until about two days after ovulation is expected.

Example 2

  • A client comes to you and asks about using the calendar method to prevent pregnancy. When you ask her about the history of her menstrual cycle over the last six months, she tells you it comes regularly every 30 days. Calculate the fertile period of your client and advise her when to avoid sex in order to prevent pregnancy.

  • Regular cycle30 - 14 = 16
    First day of fertile phase16 - 7 = 9
    Last day of fertile phase16 + 2 = 18

    Therefore, her fertile period is between the 9th and 18th days, and she should avoid sex between these days of the cycle.

Advantages of the calendar or rhythm method

This method does not require daily monitoring of fertility indicators.

Disadvantages of the calendar or rhythm method

It is associated with a high failure rate and can be difficult to use in the case of irregular menstrual cycles. It also takes a long time to learn and use it properly.

Effectiveness of the calendar or rhythm method

This method is about 95% effective if a woman uses it correctly (Family Planning: A Global Handbook for Providers, World Health Organization (WHO), 2007).

  • What can a couple do if they are not confident about using this method?

  • The couple should be advised to use additional methods, like condoms or other barrier methods, to prevent unwanted pregnancy. You should provide them with the necessary resources.

Basal body temperature (BBT) method

The basal body temperature method is based on the slight increase in the body temperature of women at rest by about 0.3–0.5°C during and after ovulation, due to the action of an increased level of progesterone secreted by the corpus luteum. The rise in body temperature sustained for three consecutive days indicates that ovulation has occurred, and it remains at this increased level until the start of the next menstrual cycle. In this section you will learn about when the rise in body temperature occurs, and what women need to know in order to use this method properly.

This natural family planning method may be selected if the woman is not willing to touch her genitalia to check her cervical secretions (as in the cervical mucus method), but is willing to abstain from sexual intercourse with her spouse for long periods of time. It is difficult for a woman to use natural family planning methods if her menstrual cycle is irregular, as it may disturb the subtle changes in body temperature and cervical secretions, as a result of hormonal effects.

Advantages and disadvantages of BBT

The advantages and disadvantages of BBT are summarised in Table 4.1 below.

Table 4.1  Advantages and disadvantages of BBT.



No side-effects for this method.

Encourages discussion about family planning between couples.

High failure rate if the couple do not clearly understand the method.

Requires several days of abstinence.

Needs a longer duration to practice, understand and use properly.

False interpretation or indications in the case of fever, as this may mislead the result of BBT.

A special thermometer may be required.

Effectiveness of BBT

BBT is about 98% effective if the woman uses the method correctly (Family Planning: A Global Handbook for Providers, WHO, 2007). But it’s still important to realise that of 100 women using this method in any one year, two will become pregnant. Its effectiveness will decrease dramatically to 80% if the woman does not use the method correctly. Effectiveness is greatest when the couple limits unprotected sexual intercourse to the period after ovulation.

Method of BBT

To use the basal body temperature method effectively, you need to know and teach women how to read a thermometer and record the results on a special chart or graph paper. Figure 4.1 shows the period of time when a couple must avoid sexual intercourse or use other protective methods.

Graph showing of basal body temperature variations during a menstrual cycle
Figure 4.1 An example of basal body temperature variations during a menstrual cycle. Note that the pattern varies in different women.
  • In Figure 4.1, on which days of the woman’s menstrual cycle does her temperature show a three-day rise?

  • It rises on days 15, 16 and 17. This indicates that ovulation has happened and passed.

If the temperature falls on or below the woman’s normal basal temperature during the three day count, that may indicate ovulation has not yet occurred. To avoid pregnancy, wait until three consecutive temperatures are recorded above the normal basal temperature.

After the beginning of the infertile phase (the third day of a rise in temperature or ‘peak day’), it is not necessary to take the temperature and it is possible to continue sexual intercourse until the first day of the next menstrual cycle.

In this regard, you should explain that the women needs to do the following:

  • Place the temperature chart and thermometer at her bedside and decide initially whether to take her temperature either orally, vaginally or rectally, and use that same method all the time.
  • Take the temperature immediately after waking up and before getting up from the bed in the morning, and before doing anything like drinking tea or coffee.
  • Shake the thermometer to lower the mercury below 35ºC and place it either rectally or vaginally for about three minutes, or orally for four to five minutes to measure her body temperature. The rectal and vaginal routes are more consistent, but the oral route is adequate if it is used consistently.
  • Read the thermometer after the required time and record the temperature; interpret whether there has been a rise in the temperature. Near ovulation, she will notice a rise of 0.3ºC‒0.5ºC.
  • Abstain from (avoid) sexual intercourse from the first day of menstrual bleeding until the temperature has risen above the regular temperature and stays up for three full days.
  • Know that after the third day (peak day) it is safe to have unprotected sexual intercourse, until the next menstrual bleeding begins.

  • How long does the ovum remain viable?

  • The ovum remains viable for at least 24 hours. It is important to note that because the woman cannot be sure exactly when she ovulated, she should be cautious about resuming sexual intercourse.

There is a lot of information in this section. You may wish to go through the basal body temperature method several times so that you are confident that you can explain it to couples who wish to practise this method. They will be more likely to follow the procedure carefully if they understand what is happening in the woman’s body.

Cervical mucus method (CMM)

The cervical mucus method (or Billings method) is based on the recognition and interpretation of changes in cervical mucus and sensations in the vagina, due to the effect of changes in oestrogen levels during the menstrual cycle. This method is also an ovulation method used by women trying to get pregnant and have a child.

Mechanism of action of CMM

You may remember from the description of natural family planning methods, that the rise in the level of oestrogen during the menstrual cycle influences the cervical gland to secrete mucus that changes from a sensation of dryness in the vagina (characterised by thick, viscous and sticky mucus), to a sensation of wetness in the vulva (characterised by thin, white, slippery and stretchy thread-like, transparent strands — similar to uncooked egg white), during ovulation.

Using this method, these are the times when it is safe to have sexual intercourse:

  • After menstruation ends the dry days (absence of cervical secretions) will start, and during these days it is safe to have sexual intercourse every other night until a woman starts to feel wet in her vagina. Every other night is suggested, as it will help women from confusing semen with cervical mucus.
  • It is also safe from the evening of the fourth day after the peak day, to the beginning of the next menstruation. Once a woman has ovulated, her cervical mucus will begin to dry up, so the peak day is the last day of cervical or vaginal wetness.

Effectiveness of CMM

The effectiveness of the cervical mucus method is about 97% if women use it correctly (Family Planning: A Global Handbook for Providers, WHO, 2007). The conditions which can affect correct use are summarised in Box 4.2.

Box 4.2  Conditions affecting the cervical mucus pattern in women

  • If a woman has a vaginal or cervical infection.
  • If a woman has recently had sexual stimulation (which will increase vaginal secretions).
  • If a woman is currently taking drugs for colds or sinusitis, which may dry up mucus secretions.
  • If a woman is in physical or emotional stress.
  • If a woman is currently breastfeeding.

Advantages of CMM

The advantages of this method are similar to those associated with the use of the basal body temperature method.

Disadvantages of CMM

CMM has a high failure rate because it needs several days of abstinence and a lot of experience in using the method to be effective. It is also difficult to use this method in the case of vaginal infections, as the cervical mucus secretions may be misleading.

Method of CMM

You will need to carefully instruct women to be able to:

  • Use a chart to record their mucus pattern.
  • Look at their cervical mucus in the morning, and every time after using the toilet, using a clean cloth or tissue paper to determine the colour and consistency of the mucus.
  • Touch the secretion to determine its stretchiness and slipperiness (see Figure 4.2).
  • Feel how wet the sensation is in their genitalia when they are walking.
  • Abstain from sexual intercourse on the day when mucus appears, regardless of its consistency, until the third evening after the ‘peak day’ (see Table 4.2).
Diagrammatic illustration of slippery and non-elastic cervical mucus.
Figure 4.2  Diagrammatic illustration of slippery and non-elastic cervical mucus.

Table 4.2  Observations of cervical mucus, and how to interpret when sexual intercourse is allowed. (Source:  Family Planning Methods and Practices: Africa, Second Edition, 1999, p.485)

Approximate day of menstrual cycle (phase)How to identifyIntercourse allowed?
1‒5: Menstruation*BleedingNo
6‒9: Dry daysAbsence of cervical mucusOn alternate nights only, to avoid confusion between mucus and sperm
10: Fertile dayOnset of sticky mucus secretions (gradually becoming slippery over the following days)No
16: Peak fertile dayLast day on which slippery mucus (resembling raw egg white) is observedNo
20: Fertile period endsEvening of the fourth day after the peak dayAfter fertile period ends
21‒29: Safe period (dry days)From end of fertile period until onset of bleedingYes
* The cycle begins on the day of menstruation.

4.2  Types of natural family planning methods

4.2.2  Lactational amenorrhoea method (LAM)