[ noun ] natural family planning in which ovulation is assumed to occur 14 days before the onset of a period (the fertile period would be assumed to extend from day 10 through day 18 of her cycle)

Used in print

(The Rev. John A. O'Brien, "Let's Take Birth Control...)

The Roman_Catholic_Church sanctions only abstention or the rhythm_method , also_known_as the use of the infertile or safe period .