Ovulation is the point in your menstrual cycle where one of your ovaries releases an egg. Typically an egg survives in the female reproductive system for between 12 and 24 hours, this varies cycle to cycle. Natural Cycles works by detecting ovulation, this can be identified by an increase in basal body temperature caused by hormones prior to ovulation day. Basal body temperature is the lowest resting body temperature measured to 2 decimal points. Read more about how Natural Cycles works here.
In biological terms, your ovulation day is the only day when you can get pregnant, as this is the point when the sperm and the egg actually meet. However, it’s really important to know that you are fertile before this! It’s not enough to avoid unprotected sex on your ovulation day as there is still a risk of pregnancy, this is due to – yes you guessed it – sperm survival.
Sperm survival varies due to a number of factors. You need to know that the maximum amount of time sperm can live in a woman’s reproductive system is 5 days. Some sperm will live for a shorter time, depending on the conditions in the vagina, fallopian tubes and uterus. (Such as the consistency of cervical mucus.) Without the right ‘fertile conditions’, sperm will die within a few hours.
You can make a note of your cervical mucus when you input data into the Natural Cycles app, but this won’t be used by the algorithm to calculate your fertility. Want to know more about the look and feel of the app? Check out the app interface and different views.
So now we know that in the right conditions, sperm can live for up to 5 days. With this in mind, we can calculate the fertile window to be 6 days long. This includes the 5 days sperm can survive, plus the one day of ovulation.
Once Natural Cycles has identified your ovulation day, the algorithm will also take sperm survival into account meaning you will always get at least 5 red days prior to your identified ovulation day. You will get more red days if the algorithm is still getting to know you and your unique cycle, which can take time as well as consistent measuring.
Read up on the scientific research behind Natural Cycles to find out more about how we calculate your fertile window.
The menstrual cycle is complicated, but it’s key to remember that a woman can’t get pregnant every day of her cycle. In fact, she is only fertile for 6 days, the day of ovulation and 5 days prior to that due to sperm surviving in her reproductive system before ovulation takes place.
It’s this identifiable fertile window, paired with a detectable rise in body temperature around ovulation, that makes fertility tracking possible and digital contraception an option for thousands of women.
Natural Cycles works best for women with regular menstrual cycles who are willing to commit to a routine which involves measuring body temperature most days and adding it to the birth control app. Think Natural Cycles could be the right birth control method for you?