Correct Use of Fertility Tracking Method Matches the Pill

HEIDELBERG, Germany, Feb. 22 -- A natural family-planning method based on fertility self-monitoring may be as effective as hormonal contraception but only when used correctly, researchers said.

The natural method produced an unintended pregnancy rate of 0.43% per year for couples who abstained from sex during fertile times, reported Petra Frank-Herrmann, M.D., of the University of Heidelberg, and colleagues, online in Human Reproduction.

This reflected a "correct-use" failure rate comparable to the 1% rate per year for the birth control pill, they said.

However, when "incorrect use," such as unprotected sex during fertile times, was added to the calculation, the unintentional pregnancy rate rose to 1.61% per year for the overall cohort of 900 couples.

The symptothermal method, as it is called, used temperature and cervical secretion measures to identify the beginning and end of the fertile period.

The findings came from a cohort of 900 volunteers in a larger prospective, longitudinal study that started in 1985. The women were all new users of the fertility awareness method and received training in small groups through the German Natural Family Planning study center that coordinated the study.

Inclusion criteria were intention to avoid pregnancy at baseline, willingness to document all sexual behavior including occasional use of barrier methods, no contraception use other than barrier methods, no younger than 19 at entry or older than 46 at the end of the study, average cycle length between 22 and 35 days, no previous history of infertility, and willingness to participate for at least 12 menstrual cycles.

During the first year, for example, the guidelines for identifying the first fertile day of each cycle were to look for the first appearance of cervical secretion and to calculate it as the sixth day of the cycle

To identify the last fertile day, the women were instructed to look for the evening of the third day after the cervical secretion peak day and the evening of the third higher temperature reading.

Women submitted their menstrual cycle charts recording basal body temperature, quality of cervical secretions, cycle length, family planning intention, and sexual behavior after each cycle was completed. Overall, 15 unintended pregnancies occurred at two years from baseline.

The researchers found that 322 women used only the fertility awareness method, while 509 women combined it with occasional use of barriers during fertile times.

The outcomes after 13 cycles (one year) were:

• Overall, 1.79 per 100 women became unintentionally pregnant (standard error 0.52). All unintended pregnancies due to method and user failure were included.
• 1.62 per 100 women became unintentionally pregnant who abstained from sex during fertile times (standard error 0.89) compared with 2.02 per 100 who used barrier methods with intercourse during fertile times (P>0.60).

The researchers said they were surprised by the low failure rate with barrier use, which was comparable to abstinence only during fertile times.

Obviously, couples with fertility awareness are more likely to use condoms more consistently in the fertile time, they wrote.

The rates of unintended pregnancy were:

• 0.43% per year in a "perfect use scenario" of abstinence during the fertile time (0.43 per 100 women per year, 95% confidence interval 0.05% to 1.55%);
• 0.59% per year for those who did not have unprotected sex during a fertile time (CI 0.07% to 2.13%);
• 7.46% per year for those who had unprotected intercourse in the fertile time (CI 4.15% to 1.23%, P<0.00001 versus abstinence);
• 2.18% per year for any intercourse in the fertile time (CI 0.27% to 7.65%);
• 1.61% per year overall (CI 1.01% to 2.43%).

On the basis of these data, the researchers concluded that the symptothermal method is a highly effective family planning method, provided there is consistent adherence to the appropriate guidelines.

For a contraceptive method to be rated as highly efficient as the hormonal pill, it requires a failure rate of less than one pregnancy per 100 women per year, Dr. Frank-Herrmann and colleagues wrote.

"We therefore maintain that the effectiveness of the symptothermal method investigated in this study is comparable to the effectiveness of modern contraceptive methods like oral contraceptives," they added.

Referring to the "surprisingly low" 7.5% pregnancy rate for couples who had unprotected intercourse during the fertile time (compared with 28% per cycle for women trying to get pregnant), the researchers said this may have been due to couples hedging their bets with intercourse at the margins of the measured possible fertile time.

"Therefore, we recognize that some of the couples were practicing conscious intelligent risk taking," they wrote. However, they added that one cannot compare the pregnancy rate on possibly fertile days--derived from couples who explicitly wanted to avoid a pregnancy and therefore practiced intelligent risk taking--with pregnancy rates derived from intention to get pregnant.

Almost 70% of couples remained in the study for at least 12 cycles, although less than 25% stayed for more than 24 cycles.

The researchers said this represents a relatively low dropout rate for a natural family planning method, but they cautioned that such methods require more engagement on the part of couples compared with oral contraception.

They also cautioned that efficacy rates may vary in real-world use because the use of volunteers and cultural backgrounds may affect motivation to avoid pregnancy.

Summing up, the investigators said, "To be able to make an informed choice when selecting a family planning method, couples need to know the efficacy of a method when used consistently and imperfectly."