Efficacy of cervical mucus observations plus electronic hormonal fertility monitoring as a method of natural family planning

J Obstet Gynecol Neonatal Nurs. Mar-Apr 2007;36(2):152-60. doi: 10.1111/j.1552-6909.2007.000129.x.


Objective: To determine the effectiveness of an electronic hormonal fertility monitor plus cervical mucus monitoring to avoid pregnancy.

Design: A 12-month prospective clinical efficacy trial.

Setting and participants: One hundred ninety five (195) women (mean age 29.8 years) seeking to avoid pregnancy with a natural method at 5 clinical sites in 4 cities.

Intervention: Each participant was taught to track fertility by self-observation of cervical mucus and an electronic monitor that measures urinary levels of estrone-3-glucuronide and luteinizing hormone.

Main outcome measures: Correct- and typical-use unintended pregnancy rates.

Results: There were a total of 26 unintended pregnancies, 3 with correct use. With 1,795 months of use, the correct-use pregnancy rate was 2.1% per 12 months of use (i.e., 97.9% effective in avoiding pregnancy when rules of the method were always followed) and the imperfect-use pregnancy rate was 14.2% per 12 months of use (i.e., 85.8% effective in avoiding pregnancy when rules of the method were not always followed and all unintended pregnancies and months of use were included in the calculations).

Conclusions: Correct use of an electronic hormonal fertility monitor with cervical mucus observations can be as effective as other fertility awareness-based methods of natural family planning. Comparative studies are needed to confirm this conclusion.

Publication types

  • Clinical Trial
  • Multicenter Study

MeSH terms

  • Adult
  • Biomarkers / analysis
  • Cervix Mucus / physiology*
  • Female
  • Humans
  • Menstrual Cycle / psychology*
  • Natural Family Planning Methods / methods*
  • Ovulation Detection / methods*
  • Pregnancy
  • Pregnancy, Unwanted
  • Prospective Studies


  • Biomarkers