Natural family planning is relying on your own fertility awareness, which is the knowledge of when you’re most likely to get pregnant in your menstruation cycle. From technologically-advanced digital thermometers, kits that measure hormones in your urine, and smartphone apps, there are plenty of tools to aid you in your journey. But while major advances in science have given us a better understanding of fertility and ovulation, natural family planning comes back to the basics – charting your menstrual cycle on the calendar.

Reference: http://www.mayoclinic.org/healthy-lifestyle/birth-control/basics/natural-family-planning/hlv-20049454/