What changes does the progesterone-only pill cause in cervical mucus?

The progesterone-only pill, also known as the mini-pill, primarily works by thickening the cervical mucus. This change in cervical mucus is significant as it creates a barrier that is less permeable to sperm, thereby reducing the chances of fertilization. The thickened mucus serves to obstruct sperm passage and can also help in preventing the sperm from reaching the egg in the event of ovulation.

The thickening of mucus occurs due to the effects of progesterone, which promotes the secretion of mucus that is more viscous than that produced during the follicular phase of the menstrual cycle when estrogen levels are higher. This physiological change is crucial for the contraceptive action of the pill, making it an effective option for preventing pregnancy.

Other options, such as thinning of the mucus or causing no change, do not accurately reflect the biological effects of progesterone on cervical mucus. Increased sensitivity may refer to changes in cervical tissue sensitivity but does not directly relate to the primary function of cervical mucus in the context of the progesterone-only pill.