Luteal phase

The luteal phase begins after ovulation, when the 'yellow body' (corpus luteum) is formed from the Graafian follicle. The cells of this body produce a large amount of progesterone, which acts on the lining of the uterus and supports the implantation and retention of the fertilised egg - embryo. If fertilisation does not occur, then the corpus luteum disintegrates and a rapid drop in progesterone and other hormones triggers menstrual bleeding.