Ovulation (the release of one or more eggs from an ovary) occurs within a 24 hour period and only once during a menstrual cycle.

Day 1 of menstrual bleeding is the first day of the cycle.

The time interval from day 1 to ovulation may vary.

The time interval from ovulation until menstruation is about 2 weeks.

Ovulation will occur early in a short cycle and later in a long cycle.

Observing the cervical mucus symptom gives information about being potentially fertile or infertile on a day by day basis.

The fertility and infertility patterns ahead of ovulation vary from woman to woman.

Once released from the ovary, the ovum (egg) lives for 12-24 hours, unless fertilised.

Sperm cells need suitable cervical mucus to survive and reach the ovum in the Fallopian tube.

Sperm cells may live for 3-5 days in suitable cervical mucus. At infertile times they will survive in the vagina for only an hour or two.