Effectiveness and Acceptability of the Sympto-thermal Method of

Natural Family Planning in Germany

Petra Frank-Herrmann
Gunter Freundl
Siegfried Baur
Michael Bremme
Gerd K. Döring
Erhard A.J.
Godehardt and Ursula Sottong
Dusseldorf, Munich and Bonn, Germany

In 1985 a representative public opinion poll showed that in Germany about 4% of women aged 15-45 were using NFP.

The main reason given for adopting NFP is dissatisfaction with other contraceptive methods or fear of side effects.

A prospective study supported by the German Ministry for Youth, Family, Women and Health studied the use-effectiveness and acceptability of symptothermal NFP, the sexual behaviour of the users, and the proportion of NFP-only users ('NFP users') to those using barrier methods in the fertile phase ('mixed method users').

It also investigated how many couples wishing to avoid pregnancy have intercourse in the fertile phase without contraceptive protection.

The study began in 1984 and is still in progress as a joint project of the University of Dusseldorf and the Arbeitsgruppe NFP, Bonn.

Material and methods

The study participants and, when possible, their partners, have been instructed in small groups by about 500 NFP teachers in the symptothermal method of self-observation of cervical mucus and basal body temperature to define the beginning and end of the fertile phase.

The women's observations are entered on a specially developed cycle chart.

The woman also records sexual behaviour including protected and unprotected intercourse and other forms of genital contact.

In addition, the client states on each chart whether or not she wants to become pregnant in the next cycle.

Pregnancies are classified as 'intended' or 'unintended' on the basis of the statements made before conception.

To enter the effectiveness study, participants must be aged 20-45 and have a cycle length of 25 to 35 days.

All women who request NFP are taught, including women with irregular cycles, post-pill and pre-menopausal women, breast feeders, post-miscarriage and women trying to conceive.

Some participants move from one category to another during the study.

There were no significant differences in age, educational level, completed family size (spacer/limiter), previous unintended pregnancy, experience with other family planning methods or religion.

The data are collected on a purpose-built computer programme which is also used for statistical evaluation and administration.


Altogether there are 851 women with 12,765 cycles in the study.

Of these, 506 women with a total of 6891 cycles met the conditions of the effectiveness study.

Of these, 241 women with 3007 cycles used NFP only for family planning and 265 women with 3884 cycles occasionally used barrier methods, mainly the condom, in the fertile phase.

The educational level of NFP clients tends to be higher than in the general population.

One reason for this is that NFP information is obtained through books and other specialised sources; little can be obtained via the media or medical profession.

The participants are relatively young, with 67% between 19 and 29 years old, and almost half are childless.

73% of the women with children are spacing while 18% have completed their families and are limiting.

The 'lost to follow-up' rate is 2.6% and lack of continuation because of dissatisfaction and problems with NFP is 7.1%.

In the use-effectiveness study for NFP-only users, we found four unintended pregnancies in 3007 cycles - a Pearl index of 1.6.

For mixed-method users, there were six unintended pregnancies in 3884 cycles - a Pearl index of 1.9.

Of the 13 unintended pregnancies (see note below), 3 were method failures

while the other 10 occurred in cycles in which unprotected intercourse took

place during the fertile phase.

Many user-related pregnancies occur because couples who generally refrain from intercourse in the highly fertile phase often risk unprotected intercourse at the beginning of the fertile phase.

Two of the method failures were among the NFP-only users.

In both cases pregnancy resulted from intercourse on Day 5 of the cycle, in one case 7 days before the temperature rise and in the other case 5 days before the rise.

The third method failure occurred in the mixed-method group when there was no intercourse in the fertile phase.

Note: Women with a cycle length of less than 25 days or more than 35 days are often excluded from effectiveness studies because of the assumption that they have reduced fertility.

However, we found that women with short cycles have fully adequate cycles with early ovulations and sufficiently long luteal phases (ie. high-temperature phase of 10 days or longer).

Only cycle lengths of less than 22 days are often connected with signs of subfertility.

The high fertility of women with short cycles has been shown by the relatively high number of unintended pregnancies among them, and we therefore included them in the use-effectiveness study.

Therefore, for the NFP-only user there were two more unintended pregnancies in 167 cycles and for mixed-method users one more unintended pregnancy in 111 cycles.

The Pearl Index for NFP only users (with a cycle length of 22 to 35 days) was 2.3 and for mixed-method users was 2.1

Analysis of NFP Only Users - (262 users)
Sexual Behaviour in the Fertile Phase
No Intercourse7012.5
Occasional Unprotected Intercourse19234.2
Failure Rate - NFP Only Users
Number of Women262
Number of Cycles3,208
Number of Unplanned Pregnancies7
Pearl Index2.3
Analysis of Mixed Method Users - (298 users)
Sexual Behaviour in the Fertile Phase
Occasional Protected Intercourse6311.3
Occasional Protected and Unprotected Intercourse23542.0
Failure Rate - Mixed Method Users
Number of Women298
Number of Cycles4,196
Number of Unplanned Pregnancies8
Pearl Index2.1
What is surprising about this table is that
those to whom occasional barrier use was acceptable
still had unprotected intercourse in the fertile phase.

Use of barrier methods does not reduce additional risk-taking!

Table 1

Significant differences between consistent and inconsistent users
Consistent Users
Inconsistent Users
Working or training / housewife
69 / 31
53 / 47
Unmarried / married
44 / 56
26 / 74
No child / one or more children
62 / 38
46 / 54
This table shows that unmarried women who work or study outside the home
and have no children are more likely to be consistent users.

Married housewives with children were more likely to take risks.

The consistent users may have been more motivated to avoid pregnancy.

Table 2


German NFP users frequently took risks and had unprotected intercourse in the fertile phase, but mostly broke the rules at the beginning of the fertile phase when the risk of pregnancy was relatively low.

The use-effectiveness of the symptothermal method examined is very good.

The low drop-out rate shows good acceptance.

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