God blessed them and said to them, “Be fruitful and increase in number; fill the earth and subdue it. . .” Genesis 1:28

Before Adam and Eve sinned, God told them to have babies. To have babies, the woman’s body needs to prepare for impregnation. To do that, she needs to menstruate.

Menstruation is not a sin nor the result of sin. However, the pain associated with menstruation (cramping, moodiness) may be a by-product of God’s consequence on women to experience pain during pregnancy.