Research library
Evidence over anecdote.
Each entry summarizes a study, explains why it matters, and is honest about its limitations. Original sources are linked throughout.
New to the science?
If you are still getting oriented, start with the basic guides that explain what NFP observes and how effectiveness claims should be read.
Human Reproduction
2007
Effectiveness of the Sensiplan sympto-thermal method
A prospective German cohort study of women using the Sensiplan double-check sympto-thermal method, often cited when discussing how effective a well-instructed fertility awareness based method can be when learned from a trained instructor.
Journal of the American Board of Family Medicine
2013
Marquette Method postpartum and breastfeeding research
A clinical study of a Marquette Method postpartum protocol that combines urinary hormone monitoring with cervical mucus observations to help breastfeeding women identify the return of fertility after childbirth.
Journal of the American Board of Family Medicine
2016
How accurate are fertility tracking apps
A review of consumer fertility tracking apps that examined how well they identified the fertile window when used to avoid pregnancy. The findings explain why apps vary so much and why the underlying method matters more than the interface.
Human Reproduction
2000
Urinary LH monitoring and ovulation timing
A study comparing a home urinary hormone monitor against transvaginal ultrasound and serum hormone measurements to see how well urine-based testing reflects ovulation timing.
Contraception
1997
The Lactational Amenorrhea Method (LAM)
A multicenter clinical study of the Lactational Amenorrhea Method, the structured use of full breastfeeding in the first six months postpartum as a temporary way to space pregnancies. The study informs the criteria still used today.
Fertility and Sterility
1981
WHO multicentre trial of the Billings Ovulation Method
A multinational trial coordinated by the World Health Organization that tested how well women across several countries could be taught the Billings Ovulation Method, a fertility awareness based approach that uses cervical mucus observations.
Journal of Reproductive Medicine
1999
Creighton Model charting and pregnancy probabilities
Research describing how the Creighton Model FertilityCare System uses standardized cervical mucus observations to identify fertile and infertile days, and what is known about pregnancy probabilities for users following the protocol.