Fertility is your chance of getting pregnant.
If you are fertile, you are likely to get pregnant — when you have sex without contraception. If you are not fertile, you are not likely to get pregnant. Most people are more fertile, and less fertile, at different times in their menstrual cycle.
If you want to get pregnant, it is best to have sex when you are fertile. If you don’t want to get pregnant, it’s best to have sex when you are not fertile. Either way, it’s really helpful to understand how your menstrual cycle affects your fertility.