Your body’s hormones control the menstrual cycle. When the level of the oestrogen hormone in the body increases, the ovaries will release an egg (ovulation).
In the second half of the cycle, the levels of progesterone hormone will increase and this gets the womb ready for pregnancy.
If pregnancy doesn’t occur, oestrogen and progesterone levels will drop. This hormonal change causes the lining to be shed from the womb which causes a period.
periods and pregnancy.pdf – Easy Read