Before you can estimate the days a woman is most fertile, it helps to understand how the body changes during a menstrual cycle, particularly in relation to the various
physical signs. By starting from day one (the first day of a menstrual period) you can record your findings on a
fertility chart to assist with conceiving a baby.
This section describes each phase of the menstrual cycle in relation to the possible changes in Basal Body Temperature, vaginal mucus and the cervix as well as some common emotional signs during each phase. We will also describe the physical signs that may occur if a baby is conceived that month.
NOTE: This information is based on a 28 day menstrual cycle. However, if you are not experiencing a regular 28 day cycle, we provide examples of adjustments you need to make if your cycle is longer or shorter. Be aware that different cycle lengths change the timing of the estimated fertile days, so you can't always rely on just 'counting the days'. This is why other physical signs are taken into account.
Bleeding phase
Pre-fertile phase
Fertile phase
Releasing an egg (ovulation)
Post-fertile phase
Bleeding phase
The start of the bleeding phase (or period) is Day 1 of the menstrual cycle. The medical term for a woman's period is menstruation, coming from the Latin word
mensis meaning month. Bleeding patterns are very individual for each woman and can last from 2 to 8 days but on average are 4 to 6 days.
The ovaries produce two hormones to regulate the menstrual cycle - progesterone and oestrogen (or estrogen - US spelling). Both oestrogen and progesterone are at their lowest levels during the bleeding phase.
The first day of bleeding is written as 'day 1' on your
fertility chart. However, you do not need observe anything else at this stage. Just put the letter B in the mucus column to indicate you are bleeding.