The menstrual cycle is divided into two phases:
- The first phase is also known as the "Follicular Phase" and it starts on the first day of your menstrual period, the day your bleeding or period begins, called cycle day one or CD1, and lasts until ovulation.
- The second phase is known as the "Luteal Phase" and begins on the day after ovulation occurs and continues until the day before your next menstrual bleeding, indicating the start of your next period.
The length of the follicular phase can normally last between 7 and 21 days, but the luteal phase needs to last a minimum of 12 days to ensure that the fertilized egg has enough time for implantation. Having a normal luteal phase is essential for your fertility.