When are you most fertile needs to be answered with two trails of thought. Firstly, your most fertile time in life, of course age related. And then your most fertile point within your monthly cycle.
When are you most fertile within your lifetime?
So when are you most fertile? According to the American Society for Reproductive Medicine, you are most fertile aged between 20-24.
As I’m sure you will recall from your high school lessons in reproduction, your ovaries contain sacs named follicles, which house eggs ready for development and release. Monthly, within your cycle, the pituitary gland located in the brain creates a hormone that causes the growth of a section of these follicles. As these follicles grow, one will reach maturity and rupture resulting in the release of an egg (ovulation) ready for fertilisation.
The remaining follicles that began the process will cease growing and degenerate. Men will go on producing sperm throughout their lives; women on the other hand don’t produce any more egg bearing follicles, they are born with all they will ever need stored within the ovaries. While there are plenty to keep you going, there’s not enough to last you a lifetime. Only a few, of the millions of follicles you are born with will ever reach maturity and release an egg. The rest will go through degeneration within the natural process of a woman’s reproductive life.
And it’s this aspect that results in fertility decreasing with age.
With many women choosing to start families later in life for reasons such as career aspirations, your diminishing fertility could become a factor when trying to become pregnant. Each woman is different, but there is an upper limit to your body. If you are older than this age range, it doesn’t necessarily mean you are no longer fertile, it’s just not when you are most fertile.
When are you most fertile in your monthly cycle?
To determine when are you most fertile, you must understand the processes involved in your monthly cycle. Here’s a quick recap for those unsure.
A woman’s menstrual cycle usually occurs regularly every 26 to 35 days, with the average being 28 days.
The phrase ‘monthly cycle’ can be a little misleading, remember it is the rolling day count. You may consider yourself as having irregular periods as they don’t happen at the same time each month, but remember they can be as high as 35 days in length. So be sure to count days rather than dates.
In this example we use a 28-day cycle (for easier math). The process begins with an egg being released from a follicle in the ovary. After release, if this egg is unfertilised, after around 12 to 14 days will see the start of a menstrual bleed in order to discharge the unfertilised egg.
Day one of the menstrual bleed is the ‘first day of your cycle’. You should expect your next period/cycle in 28 days time. This means on an average 28 cycle you will likely ovulate around day 14. You are most fertile on the day of ovulation and up to 5 days before.
For the best timing to conceive you are advised to have sex on your most fertile day, your day of ovulation. Since sperm live for a few days you are also advised to have sex every other day leading up to ovulation, so for example on days 10, 12 and 14 of your cycle (if your cycle is an average 28 days).
However, it is important that you know this is just an example.
While it is correct you are most fertile on the day of and just before ovulation, there are a lot of assumptions made to the ovulation day being day 14. Every woman is different. Sure on average it will be day 14, but it could be as early as day 10 or as late as day 20. Imperative in determining when are you most fertile, is knowing for sure when you are going to ovulate.
There are a few ways to track when you are going to ovulate, which you can read more about here.