Mucus Cycle

The Mucus Cycle is the run of fertile-type cervical mucus within a single menstrual cycle. It begins at the Point of Change and ends on Peak Day. The Point of Change marks the first observable departure from the dry baseline. The mucus cycle is the estrogen-driven core of the fertile phase.

The charted fertile window extends beyond Peak Day. It closes only after the post-Peak rule of the method confirms that ovulation has passed.

The mucus cycle differs from the mucus pattern. The mucus pattern is the full sequence of charted cervical observations across the entire cycle. It includes the dry days before Peak, the mucus cycle itself, and the dry days after Peak.

Hilgers documented this structure in The NaProTECHNOLOGY Revolution. He charted the mucus cycle as a distinct, bounded phase between menstruation and post-Peak dryness.¹

The length and character of the mucus cycle vary. A short or atypical mucus cycle can point to low estrogen, cervical factor infertility, or cycles that are approaching anovulation, the absence of ovulation. Charting the mucus cycle over several months reveals patterns that a single cycle cannot demonstrate.