Fertility Awareness · Methods

The risks of the natural family planning methods

Zufferey MM

Published May 1986 Therapeutische Umschau. Revue Therapeutique, 43(5), 417-424
PMID 3726778
Read our synopsis

RRM Academy Synopsis

Natural family planning carries a risk of pregnancy, a review argues

Critical to restorative reproductive medicine

A review of five natural family planning methods argues that the main risk of these methods is pregnancy from method failure or user error. The author covers calendar, temperature, Bioself thermometer, mucus and symptothermal methods. The abstract lists no patients and no new data.

Key Findings

  • The author says the symptothermal method has high effectiveness rates, with pregnancy risks generally the same as those of the mucus and temperature methods.
  • The author reports that some authors found flat, one-phase temperature curves in 3-20% of cycles in which ovulation occurred.
  • The author says the Bioself thermometer, which stores the 6 most recent cycle lengths for cycles of 19-39 days, has no formal evaluation in the literature.
  • The author says the calendar method, based on the past 6-12 cycles, was seldom taught at the time of writing because it fails often.
  • The author names four routes to pregnancy: method failure, poor instruction, user error, and failure to abstain through the whole fertile period.

Interpretation

The source is the abstract of a 1986 narrative review, meaning an expert's survey of the literature. The abstract cites figures from other authors and gives no study population or sample size. The author says a theoretical higher risk of miscarriage or fetal malformation from aging egg or sperm cells at conception has not been definitively evaluated. The author says comparisons of efficacy between methods are difficult.

RRM Context

Restorative reproductive medicine uses cycle charting to understand ovulation and find root causes, with evaluation before treatment. This review addresses natural family planning to avoid pregnancy. The author raises unstandardized temperature rules and signs that other conditions can alter. Both issues bear on how charting is taught and read.

Abstract

Risks of 5 natural family planning (NFP) methods are compared. The main risk of these methods is the risk of pregnancy stemming from method failure, errors in instruction, error in application of the method, and failure to observe abstinence during the entire fertile period. The calendar rhythm method, the oldest NFP method, is based on calculation of likely fertile days in the preceding 6-12 menstrual cycles. The method is seldom taught at present because of its high failure rate, but it continues to be used, often by individuals with an incomplete understanding of the calculations. The principle of the basal body temperature method is well known. The thermal shift affirms the beginning of the infertile period but does not allow prediction of ovulation. Instructions provided by different organizations to identify the third day of the hyperthermal plateau are not standardized; the various interpretations applied to the same cycle do not necessarily lead to identification of the same day as the start of the infertile period. Comparisons of efficacy between methods are therefore difficult. Well-conducted prospective studies have demonstrated high theoretical efficacy, but failure rates in practice appear to be higher. Women often do not know how to interpret a temperature curve correctly, and the curve may be influenced by illness, sleeping late, a change of life style or thermometer. Some authors have reported that 3-20% of ovulatory cycles have monophasic temperature curves. The temperature method requires lengthy abstinence lasting until the third day of higher temperature, which may create conflicts in some couples. To ease the difficulties of interpretation of the temperature method, a Swiss architect developed an electronic thermometer programmed according to rules of the calendar rhythm method for cycles of 19-39 days. The woman's 6 most recent cycle lengths remain in the memory to indicate probable infertile days. Although no formal evaluations have appeared in the literature on the Bioself thermometer, the method appears to entail risks including registration of incorrect temperature due to humidity or rundown batteries, and inadequate programming to identify the safe period. The Billings or cervical mucus method is based on observation by the woman of the thickness, wetness, and other characteristics of mucus secretions in the vulva to predict ovulation. Various studies have shown high theoretical efficacy but practical efficacy is lower. Vaginal infections, some ovarian pathologies, and postpartum hormonal changes are among factors that can alter mucus patterns. The method does not confirm ovulation, and false "peak days" may occur. The symptothermal method is based on all the principles of the cervical mucus and temperature methods as well as autopalpation of the cervix and any other signs of ovulation. Effectiveness rates are high. In general pregnancy risks are the same as those for the cervical mucus and temperature methods. A theoretical heightened risk of abortion or fetal malformation common to all the methods due to fertilization of aging gametes has not been definitively evaluated. Another possible risk results from timing of abstinence at the phase of the menstrual cycle when the woman's sexual desire is likely to be greatest.

Topics

Related research

Fertility Awareness › Methods › Calendar and Rhythm Methods · Contraception › Comparative Studies › Contraception Versus Fertility Awareness
PMID 3726778 3726778 Zufferey et al. 1986, Zufferey 1986

Cite this article

Zufferey, M. M. (1986). The risks of the natural family planning methods. Therapeutische Umschau. Revue therapeutique, 43(5), 417-424.