The application of the Home Ovarian Hormone Monitor to the avoidance of pregnancy by periodic abstinence has been explored. No woman had difficulty with the daily urine testing, and their results consistently identified the distinctive hormone pattern of the ovulatory cycle and the day of ovulation and correlated closely with the mucus symptoms. The tests gave 4 days or more warning of ovulation in 99% of cycles and allowed intercourse to be resumed 1 to 3 days after ovulation in 88%, giving a mean period of abstinence of 7 days. No pregnancy occurred from intercourse during the late safe days defined by the Monitor, but some early-day pregnancies occurred through long sperm survivals of 6 to 8 days, mostly during the return of fertility after breastfeeding. Rules for the avoidance of pregnancy, with the minimum of testing on the basis of these results, are given.
