The Fertile Window

Although it's the day most women dread, the day a menstrual period starts each month signifies day 1 of the menstrual cycle. For most, each cycle lasts between 26–31 days. However, some women may have longer or shorter cycles.¹

Each menstrual cycle is how the body prepares for pregnancy, and a key moment in each cycle for conception is when one of the ovaries release an egg, known as ovulation.² When ovulation occurs, the egg survives for up to 24 hours. Therefore, to have successful conception, sperm must reach the egg within this time frame.³ As sperm can survive for up to 5 days after ejaculation, the 5 days prior to ovulation, plus the day of ovulation are known as the fertile window.³

A staggering 41% of women cannot correctly identify their fertile window.⁴ In around a third of women, the fertile window is between 10–17 days of the menstrual cycle. However, in longer cycles, the fertile window will occur later and similarly will be earlier for those with shorter cycles.³ It is beneficial to track at least 6 cycles to gain an understanding of your own menstrual cycle.³ To estimate the first and last day of the fertile window, 18 days should be subtracted from the shortest recorded cycle length, and 11 days from the longest cycle length.³

Once you've determined your fertile window, there is a higher likelihood of a successful conception. In fact, the average chances of becoming pregnant vary significantly within the fertile window: ^5,6

It is important to have regular unprotected sexual intercourse every 2–3 days leading up to, and during the fertile window to increase the chances of conception.⁷

There are a number of different methods to help track and predict ovulation in the form of cycle charting apps, basal body temperature charting, fertility monitors, and ovulation test strips (using urine samples). You can speak with your healthcare provider to discuss how these may help support track your fertile window in each cycle.⁵