This question was raised by someone who recently visited the blog. It raises some fundamentally important points about human fertility and the chance of conception. It strikes me that sometimes these concepts aren’t even recognised by some doctors!
Firstly, here’s a simple truth: those couples who are most likely to get pregnant on their own, will tend to do it, within the first 6 – 12 months of trying. Usually within the first few months (for those with infertility, they are “all of your friends”, who annoyingly conceive quickly and then tell everyone else of their so-called expertise). But here’s a more interesting fact: it doesn’t matter if you are older (eg a woman above 40), if you are destined to do it on your own, it will still more likely be within the first few months of trying. In other words, it’s not that because older women have a lower chance per month and therefore it must take more months to conceive. Instead, on average older women have a lower chance per month of conceiving, but those who were going to conceive (ie those holding up the average, if you like) still conceive fairly quickly. However, there are less of them proportionately, compared to younger age groups. They then “leave behind” the rest, the majority maybe, who were always going to struggle. The problem is that you can’t immediately detect who will succeed and who will struggle, if the basic fertility tests are normal (more on tests below).
For an excellent and detailed explanation on human fertility, the monthly chance of conception, why evolution has allowed this and lots of other interesting stuff, check out Professor Robert Jansen’s book Getting Pregnant.
Now, all this assumes that there are no other problems restricting fertility other than the woman’s age (ie she ovulates, has no tubal obstructions and her partner’s sperm test is normal). However we should also factor in how long the woman has left to try (ie how acute is the age issue?).
So how do we put all this together? Firstly, whether you are younger or older, if you haven’t conceived by about 18 months to 2 years on your own, from that point on you are unlikely to (the chance is never officially zero, but it does drop to a very low likelihood per month – maybe 2-3% in the mid thirties – a success rate that you would be angry about if a doctor or naturopath was instituting a therapy with that kind of return). If you are younger (less than 37 years, say) you have time to try for about 12 months before even worrying about tests. But if you older, you have less time to spare and should consider some initial tests sooner. If the woman is above 40, I would suggest getting some simple tests without delay, as why wait for months to find out if there was a problem that should have been dealt with sooner? By these tests, I mean an ultrasound/tubal test and hormones for the woman; and a sperm test for the man. Hardly invasive tests but invaluable in determining who can keep trying with some ongoing confidence.
What if you, the woman, is 42, the tests are all normal but you have only been trying for 2 months? Surely IVF must be better than sex? No – the return from one round of IVF is lower than what you could achieve over trying for a few more months. But if you have then been trying for say 9 to 12 months without pregnancy and irrespective of “normal tests” (in fact very much if you have normal tests), if you were going to have conceived you already would have done so. You have little time left and you need help without further delay.