The proliferative phase: days 6 to 14

The concentration of oestrogen in the blood is rising during this period, following the end of menstruation, as the ovaries prepare for the next ovulation at around day 14. It is called the proliferative phase ('proliferate' means to 'multiply or increase'), because in this period the endometrium grows thicker and becomes more richly fed by blood vessels in preparation for the possibility of fertilisation and pregnancy.