Self-assessment of the cervical pupil sign as a new fertility-awareness method.

This pilot study investigates in a group of 20 healthy volunteers with regular cycles and prior experience in natural family planning methods whether self-assessment of the cervical "pupil sign" is feasible and can be used to detect the preovulatory fertile window. All participants were able to assess the cervical pupil sign. Based on this method, the fertile window lasts on average 3 days, which is significantly shorter and more consistent than when defined on basis of the vulvar mucus method.