Do you know how these percentages are arrived at? What raw data are they using?
I don't think anybody is disputing that fertility declines with age.
But when you look at this chart and you say, for example, that a woman aged 37-39 has a 67.4% chance of conceiving within 12 cycles, what exactly does that mean?
Is this hypothetical woman 37, 38 or 39? There is a difference.
By 12 cycles, do you mean 12 perfect 28 day cycles? Or a year of trying, which may be 13 cycles for a woman with perfect 28 day cycles, or fewer than 12 cycles for a woman with long cycles?
Has this woman just stopped contraception and started having unprotected sex whenever she feels like it? Or is she tracking her ovulation and hitting the right days every single time?
What's your starting point? Do you count cycle 1 from when she stops contraception? Are you controlling for women who have just stopped using condoms, women who have had a non hormonal coil taken out, and women who have recently stopped using hormonal contraception and whose cycles might take some time to regulate?
What are you counting as conception? Does a miscarriage count as a conception or only a full term pregnancy?
There are too many variables. We don't have the data to know whether these figures are reliable.
And that's before you address very basic issues such as the fact that you're lumping 34 year olds in with 36 year olds and 37 year olds in with 39 year olds, and the fact that probably the best information they have is how long women of this age self report that they have been trying, except that many women lie about how long they have been trying in order to access fertility treatment sooner. You literally just advised the OP to do exactly that.
Now if, as I suspect, these figures are based on women of varying ages who have self reported how many cycles they have been trying to conceive for, they probably aren't accurate and give a rather negative prognosis when the reality is probably more positive.
If a woman in her late 30s who has stopped contraception and whose cycles have had a chance to regulate tracks her cycles and is able to confirm that she is ovulating and has sex 2-3 times during every fertile window, including either one day or two days before ovulation, I reckon her chances of getting pregnant within a year are significantly higher than 67%.
That's why "just relax and don't track your cycles" is the worst advice on this thread, especially for a woman in her late 30s.
Some of the women you refer to who conceive naturally in months 12-24 are undoubtedly less fertile than they would have been ten years ago, but they might have conceived earlier if they had been properly tracking their cycles. A lot of women rely on apps such as Clue to tell them when to have sex. If I'd done that I would have missed my fertile window every single time. Even some of the women who end up conceiving with IUI might have just been getting the timing wrong and didn't actually need fertility treatment.