Endometrial growth is divided in two phases depending on the moment of the menstrual cycle:
- starts on day 1 of the cycle until day 14, when ovulation occurs. It a estrogen-dependent phase.
- starts after ovulation, on day 15, and extends until the end of the cycle. Progesterone plays a major role at this stage. Implantation is more likely to take place on days 19-21. This period is known as implantation window.