Natural family planning as effective as the pill
July 18, 2007
The system, which predicts a woman’s fertile phase through measuring temperature and examining cervical secretions, was trialed in a study of 900 women; it showed the sympto-thermal method (STM) was as good as the pill in preventing unwanted pregnancies.
The amount of the hormones oestrogen and progesterone varies in the menstrual cycle, which alters the quantity and the consistency of cervical mucus.
Just before ovulation the secretions become clearer, wetter, stretchy and slippery, like raw egg white.
STM depends upon a precise set of rules, which take time to learn.
The first fertile day is when the woman first identifies either: 1) first appearance or change of appearance of cervical secretion, or 2) the sixth day of the cycle.
After 12 cycles, this second guideline is replaced by a calculation that subtracts seven days from the earliest day to show a temperature rise in the preceding 12 cycles.
The fertile phase ends after the woman has identified: 1) the evening of the third day after the cervical secretion peak day, and 2) the evening when the woman measures the third higher temperature reading, with all three being higher than the previous six readings and the last one being 0.2 degrees Celsius higher than the previous six.
Among those who used a barrier method during this time, such as a condom, the pregnancy rate rose to 0.6 pregnancies per 100 women per year.
Even among those women who had unprotected sex during the fertile period, the pregnancy rate was only 7.5 pregnancies per 100
women per year – around a quarter of the rate one would usually expect.
The researchers believe this was because the women probably only had unprotected sex around the boundaries of their most fertile period.
Experts agree that natural family planning is effective provided it is taught properly by a qualified instructor and carried out correctly.
Petra Frank-Herrmann, from the University of Heidelberg in Germany, who led the study, says for a contraceptive method to be
as effective as the pill, there should be less than one pregnancy per 100 women: she says where STM was used correctly, the rate was one per 250 women.
Herrmann says that demonstrates that STM is comparable as an effective and acceptable method of family planning.