London, Feb 21 The natural family planning method could be as effective as the contraceptive pill, provided it was taught properly and carried out correctly, say German researchers.

Petra Frank-Herrmann and other researchers at the University of Heidelberg assessed the natural method of family planning - also known as the sympto-thermal method (STM) - in a study of 900 women, reported the online edition of BBC News.

They found that using the natural method, which assesses fertility levels during the monthly cycle by measuring body temperature and observing cervical secretions correctly, led to a rate of 0.4 pregnancies per 100 women per year.

The lowest pregnancy rate was found among women who abstained from sex during their most fertile period, as defined by the natural method of contraception, the researchers found.

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.

For a contraceptive method to be rated as highly effective, it should lead to less than one pregnancy per 100 women per year when used correctly, the researchers said.(IANS)