During the menstrual cycle of women of childbearing age, follicles continue to develop and mature, which gradually increases the secretion of estrogen. When it rises to a certain level, it will have a feedback effect on its pituitary gland, leading to the sudden release of LH and the expulsion of mature follicles.

Scientific research has found that the physical and chemical properties of saliva will change under the influence of estrogen. Through high-power microscope observation, we can see that the crystal morphology of saliva is very similar to cervical mucus, and both of them show patterns similar to fern teeth or plant leaves. Generally, this kind of fern crystal image begins to appear 2-3 days before ovulation, and it is most clear during ovulation. After ovulation, it gradually breaks and dissolves until it becomes a punctate pattern.

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