It is easy for every woman to calculate her own fertility window, provided she knows 3 key pieces of information:

• The egg is available for fertilization for 24-36 hours after ovulation
• Sperm can survive inside the female body for up to 5 days
• Ovulation occurs approximately 14 days before the next period starts

For example, intercourse occurring 3 days before ovulation will result in ejaculation and beginning of the journey of the sperm towards the tubes. The relatively few sperm that will make it to the end, will be alive when the egg is released by ovulation and one of them will hopefully fertilize it. Therefore, one sperm is capable of fertilizing the egg even if intercourse occurs BEFORE ovulation.

Taking into account the 3 key pieces of information mentioned above, we can draw the conclusion that the fertility window starts up to 5 days before ovulation and includes the day of ovulation itself, as well as the day after ovulation – a total of 7 days.

(Of course, the above is true as long as the egg and sperm are of good quality, otherwise the fertility window may actually be narrower)

EXAMPLES
For a regular 28-day cycle, the fertility window lasts from day 9 to day 16 of the cycle.

For a regular 26-day cycle, the fertility window lasts from day 7 to day 14.

For a regular 24-day cycle, the fertility window lasts from day 5 to day 12.

For a regular 30-day cycle, the fertility window lasts from day 11 to day 18.

For a regular 32-day cycle, the fertility window lasts from day 13 to day 20.

For a regular 34-day cycle, the fertility window lasts from day 15 to day 22.

And so on…

During the fertility window, it is advisable for a couple to have intercourse every 2-3 days (after all, we are humans, not robots!)

Obviously, all of the above apply as long as the woman’s cycle is regular.

If the cycle is not regular, this may mean that ovulation is also not regular and a gynaecologist should be consulted.

However, it is also possible (but less likely) for a pregnancy to occur in women without a regular cycle, where intercourse is simply recommended every 2-3 days without trying to calculate any fertility window.