Menstrual Cycle

This is called the follicular phase. During this time, the endometrium starts to grow, the follicles on the ovary become active, and the cervical mucous begins to thin.

Ovulation takes place midcycle. Rising estrogen levels trigger the release of LH (the “LH” surge). The climbing level of LH causes the follicle to ovulate, releasing an egg. The timing of ovulation is not precise; it may occur between days 12 and 14, depending on the individual woman. That is why it is important to understand and chart your cycle (record your basal body temperature and your LH surge on an ovulation test kit).

After releasing the egg, the follicle transforms into the corpus luteum, and progesterone is released, creating a lush uterine lining for implantation. This stage of the cycle is called the luteal phase.

If there is no implantation, estrogen and progesterone levels fall.

The falling progesterone levels trigger the shedding of the endometrium.