A menstrual cycle is the time period starting on your first day of your menstrual period, the time you bleed, and it ends the day before the next next menstrual period.

The changes in your menstrual cycle are associated changes brought on by fluctuations in hormones at different times of the cycle starting with your menstrual period or bleeding, leading up to ovulation (OD=Ovulation Day) and changes after ovulation. Most menstrual cycles are 28-29 days long - a variation of a few days more or less can be quite normal and small variations from cycle to cycle is also normal.

Cycle Day 1 (CD1) of the menstrual bleeding is referred to as Day 1 of the menstrual cycle. The length of the cycle is measured from Day 1 of one cycle (bleed) to the day before day 1 of the next cycle (bleed).

Read more about menstrual cycle abnormalities.

Cycle Day What happens?
Cycle Day 1 to CD 4-5 Usually 4-5 days of menstrual period, the time when you bleed as a result from ovulation in the previous menstrual cycle and not getting pregnant.
CD 6 - OD Time between the end of the menstrual period and the first day of fertility, 5 days before ovulation
OD minus 1-5 The 5 days before ovulation, your fertile days when eventual fertilization can happen from having intercourse. The cloer to ovulation there is sexula intercourse, the more likely pregnancy will happen. The best days for intercours in order to get pregnant are 1-2 days before the day of ovulation.
Ovulation Day = OD The day when an egg is ejected from the ovary. That is also the day when the egg gets fertilized if there are surviving sperms from intercourse. The egg can survive for up to 12-24 hours after ovulation, but sperms can survive 4-5 days.
OD plus 1-14 Post-ovulation or luteal phase. The area in the ovary from where the egg was ejected produces progesterone to support possible implantation in the uterus