Couples wishing to use a natural method to avoid pregnancy
need to learn to accurately identify the phases of fertility
and infertility by observing and recording the indicators
|Disturbed night||Time zones||Gynaecological disorders|
The book 'Fertility' includes a chapter on 'Factors affecting the menstrual cycle, which looks at the effects of stress, illness and medication on the cycle.
The guidelines for avoiding pregnancy are included here for information. It is strongly advisable to use these in consultation with an experienced NFP teacher. Please note these guidelines are only relevant for women of normal fertility.
It is advisable to have a double check and to consider the onset of the fertile phase as given by the earliest indicator.
Following the period, dry days are infertile.
It is wise to restrict intercourse to alternate evenings, because the presence of seminal fluid in the vagina may mask cervical mucus.
The day on which mucus is first recognised marks the end of this phase.
Days on which the cervix is low, long, firm, closed and tilted are infertile.
The first day of change in position or texture marks the end of this phase.
Shortest cycle minus 20 = Last infertile day
The pre-ovulatory infertile phase lasts from the first day of the cycle until the last infertile day inclusive.
Earliest temperature shift minus 7 = First fertile day
The pre-ovulatory infertile phase lasts from the first day of the cycle up to, but not including the first fertile day.
The calendar calculation and the Doering rule should be based on information from at least six cycles.
After the third high temperature has been recorded provided:
On the fourth evening after peak day
On the third day after the cervix has returned to its infertile state
Using the sympto-thermal method |
The post-ovulatory infertile phase starts:
For a systematic approach to interpreting a sympto-thermal chart see:
Completed sympto-thermal chart showing correlation between all indicators of fertility.
Intercourse in the pre-ovulatory infertile phase always carries a slight risk of pregnancy. It is in this phase we consider male fertility, because in the presence of early mucus, the life of the sperm may be prolonged.
Ovulation could occur earlier than anticipated. In a very small number of women, with short cycles of around 21-24 days, or with prolonged menstrual bleeding, mucus may appear immediately after the period or even before its end. In this case intercourse during a period could lead to conception. There will be no pre-ovulatory relatively infertile phase.
Effectiveness of the post-ovulatory infertile phase
It should be emphasised that the post-ovulatory infertile phase is the safest time for intercourse for a couple wishing to avoid pregnancy. When ovulation has been confirmed there is no risk of further fertility in the current cycle.
The above sympto-thermal chart shows a normal fertile pattern. There will however be various times throughout reproductive life when fertility may be affected.
After stopping the contraceptive pill
A chapter for post-pill users including a series of charts is included in the book 'Fertlity'.
It is possible to record fertility indicators during breast-feeding and to rely on a natural method watching for the return of fertility as breast-feeding is reduced. As there may be weeks or months of infertility associated with breast-feeding, many women now rely on Lactational Amenorrhoea Method or LAM and start recording fertility symptoms again (or choose another family planning method), when indicated by this method.
A section on Fertlity Awareness and NFP post-natally and during breast-feeding is included in the book and video 'Fertliity'.
During the pre-menopausal years
If a woman has previous experience of Fertility Awareness during normal fertile cycles this can be very helpful in identifying early changes related to the pre-menopause.. It is possible to start using natural family planning at this time despite cyclic irregularities, provided a woman has the support of an experienced NFP teacher. Women who have used natural methods successfully for a number of years will need further help to interpret their charts as cycles become irregular.
Barrier users and fertility awareness
It is true that barrier methods do not need to be used on every day of the cycle. A knowledge of fertility awareness can help couples to identify the days when they are fertile, thus reducing the use of barriers to a minimum while ensuring an effective means of avoiding pregnancy. There are special considerations, however. The use of spermicides during the pre-ovulatory phase can make the recognition of the mucus symptom difficult. Some women rely more heavily on changes in the cervix. It is important that couples understand the failure rate associated with barrier use. This will vary dependent on the chosen barrier - male or female condom or diaphragm and spermicide. (see table below) As women recognise their limits of fertility and time of maximum fertility, many will choose to avoid intercourse completely during the days of peak fertility.
When considering the effectiveness of any form of family planning, the distinction must be made between:-
The practical or use effectiveness takes into consideration all users of the method, that is those who follow the method without error and also those who are less committed and less consistent in their use. It denotes the effectiveness under real life conditions - for example the sympto-thermal method has an effectiveness rate of 85-98 per cent.
Use effectiveness of family planning methods is expressed as a percentage per 100 women per year.
|· Combined pill||97% - 99%+|
|· Progestogen only pill||96% - 99%|
|· Injectables and implants||98% - 99%+|
|· Intra-uterine system (IUS)||99%|
|· Intra-uterine device (IUD)||98% - 99%+|
|· Diaphragm or cap with spermicide||82% - 96%|
|· Condom||85% - 98%|
|· NFP - Sympto-thermal method||85% - 98%|
Barrier methods require some skill and a high degree of motivation and pills are more frequently forgotten during the first year of use.
Effectiveness of natural family planning
A high degree of motivation is essential if a couple are to use natural methods of family planning successfully. They should both be in accord about their goals of family spacing or limiting. It is interesting to note that the family-spacers, those who plan more children but at a later date, are less effective in preventing pregnancy. They are prepared to take risks; whereas family limiters, those who have completed their family, are more conscientious and determined, and more successful in preventing pregnancy. This is illustrated by a 1976 Canadian sympto-thermal study which showed an effectiveness rate of 85 per cent for the family spacers but around 99 per cent for those limiting their families. (Parrenteau-Carreau, Lanctot and Rice)
The effectiveness of any form of family planning depends on the method being well taught, well understood and well applied, but this is of particular importance for natural family planning. With experience, the sympto-thermal method is a highly effective method.
Efficiency studies of Sympto-Thermal method
Advances in teaching techniques and use of multiple index methods have considerably reduced the unplanned
pregnancy rate among NFP Users. The method is however unforgiving of imperfect use.
The frequently quoted 80% efficiency dates back to a WHO trial using cervical mucus as a single indicator. (WHO - A prospective trial of the ovulation method of NFP - II The effectiveness phase. Fertility and Sterility 1981, 36; 152-8.)
The most recent study of the sympto-thermal method reported a use effectiveness rate of 97.7% (Frank-Hermann, Freundl et al, Effectiveness and acceptability of the sympto-thermal method of NFP in Germany, American Journal of Obstetrics and Gynecology, 1991, 165,pp 2052-4)
Home Kits and devices to predict fertility
PERSONA is a new personal contraceptive system launched on September 30th 1996. The system consists of a small hand-held computerised monitor and disposable urine test sticks. After extensive research, European trials have shown PERSONA to be 94% effective.
PERSONA uses the same principles as NFP, but measures hormones directly rather than the effects of the hormones on fertility indicators. The test stick identifies the start of the fertile phase by a rise in oestrogen and the end of the fertile phase by measuring the LH surge and then allowing time for ovulation and ovum survival.
The monitor displays:
The monitor plus the first month's test sticks costs £64.95 and subsequent sticks cost £9.95 per cycle.
Further information is available from the Persona line on: + 44 (0845) 608 6081
Alternatively you can access information on the World-wide Web on: www.persona.org.uk
PERSONA is not suitable :
are included in the book and video 'Fertility'.
|Indicators of Fertility||Questions|