title: The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple's sexual behaviour during the fertile time: a prospective longitudinal study.
abstract: BACKGROUND
  The efficacy of fertility awareness based (FAB) methods of family planning is critically reviewed. The objective was to investigate the efficacy and the acceptability of the symptothermal method (STM), an FAB method that uses two indicators of fertility, temperature and cervical secretions observation. This paper will recommend a more suitable approach to measure the efficacy.
  
  
  METHODS
  Since 1985, an ongoing prospective observational longitudinal cohort study has been conducted in Germany. Women are asked to submit their menstrual cycle charts that record daily basal body temperature, cervical secretion observations and sexual behaviour. A cohort of 900 women contributed 17,638 cycles that met the inclusion criteria for the effectiveness study. The overall rates of unintended pregnancies and dropout rates have been estimated with survival curves according to the Kaplan-Meier method. In order to estimate the true method effectiveness, the pregnancy rates have been calculated in relation to sexual behaviour using the 'perfect/imperfect-use' model of Trussell and Grummer-Strawn.
  
  
  RESULTS
  After 13 cycles, 1.8 per 100 women of the cohort experienced an unintended pregnancy; 9.2 per 100 women dropped out because of dissatisfaction with the method; the pregnancy rate was 0.6 per 100 women and per 13 cycles when there was no unprotected intercourse in the fertile time.
  
  
  CONCLUSIONS
  The STM is a highly effective family planning method, provided the appropriate guidelines are consistently adhered to.
authors.affiliation: Department of Gynaecological Endocrinology and Fertility Disorders, University of Heidelberg, Vossstrasse 9, 69115 Heidelberg, Germany. petra.frank-herrmann@med.uni-heidelberg.de
authors.forename: P
authors.initials: P
authors.lastname: Frank-Herrmann
authors.forename: J
authors.initials: J
authors.lastname: Heil
authors.forename: C
authors.initials: C
authors.lastname: Gnoth
authors.forename: E
authors.initials: E
authors.lastname: Toledo
authors.forename: S
authors.initials: S
authors.lastname: Baur
authors.forename: C
authors.initials: C
authors.lastname: Pyper
authors.forename: E
authors.initials: E
authors.lastname: Jenetzky
authors.forename: T
authors.initials: T
authors.lastname: Strowitzki
authors.forename: G
authors.initials: G
authors.lastname: Freundl
mesh_terms: D000328:Adult; D001831:Body Temperature; D002582:Cervix Mucus / Q000502:physiology; D005193:Family Planning Services / Q000193:education; D005260:Female; D005298:Fertility; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012252:Natural Family Planning Methods; D010061:Ovulation Detection / Q000379:methods; D017060:Patient Satisfaction; D049168:Pregnancy, Unplanned; D011446:Prospective Studies; D012725:Sexual Behavior