[Analysis of natural family planning failures. In 7007 cycles of use]

The analysis concerned 626 users using NFP in order to avoid a conception during a total of 6740 cycles. Participation in the study did not interfere with their plan of conception, and they were invited to behave, as far as possible, as though they ignored the study. Of these 626 couples, 530 were french, 61 belgian and 35 swiss. On the whole, 39.3% used birth control to limit births and 60.7% to space them.

The observed pregnancy rates are 1.13, 6.47 and 17.58 for one year in actuarial method respectively for method, method + user and total pregnancy rate. The pregnancy rate was higher for women before 35 years (RR: 3.8; 95 p100 confidence interval: 1.4-10.3), during the six months after delivery (RR: 2.5; 1.0-4.6) and, of course, for couples with inprotected sexual intercourse in fertile phase (RR: 4.8; 2.1-11.2).

NFP can be placed among methods of great theorical effectiveness. But pregnancies as a result of intercourses during the fertile phase despite its identification are frequent: couples have to be informed.