Seeing blood has always been a sign that something is very wrong. It’s important that our daughters learn that menstrual blood does not mean something is wrong. It is the result of a healthy cleansing of the inside of the uterus. It is good for us.
Illustration from I’m a Girl, Hormones!
The inside lining of the uterine cavity is called the endometrium. During the menstrual cycle, hormones from the ovaries, especially estrogen, direct the endometrium to increase the amount of tiny blood vessels. If a fertilized egg arrives in the uterine cavity during that menstrual cycle, it attaches to the endometrium and receives nutrients from fluid that has escaped the tiny blood vessels.
If the egg has not been fertilized in the fallopian tube, the unfertilized egg disappears when it arrives in the uterine cavity. This signals a change in the hormone environment of the uterus. As you can see from the anatomy figure on the right, the endometrium begins to break apart. When that happens, the tiny blood vessels that have grown inside the endometrium also break apart. The blood that escapes from the tiny blood vessels contributes to the blood that comes out with the next period.
Hopefully this is useful information for your daughter. Menstrual periods keep our endometrium healthy, and that’s a good thing.