Question

why is menstrual cycle does not take place before puberty and during pregnancy​

Answer 1

If pregnancy doesn't happen, your body doesn't need the thick lining in your uterus. Your lining breaks down, and the blood, nutrients, and tissue flow out of your body through your vagina. Voilà, it's your period! If you do get pregnant, your body needs the lining — that's why your period stops during pregnancy.

Answer 2

Answer:

here is the answer

Explanation:

during pregnancy the progesterone levels are high which inhibits the shedding of endometrial tissue. before puberty the ovaries are immature in prophase 1 stage .after delivery the huge flow of blood is due to drop in progesterone levels and increase in estrogen leading to bleeding.