The general situation is for a woman's fertility to begin to increase very soon after menstruation begins at puberty as she approaches sexual maturity, reaching its peak when she is in her early 20s.
However, by the mid to late 30s fertility begins to decrease until it eventually reaches a point where failure to conceive becomes a higher probability than conception itself.
This point will normally be around a woman's early 40s, when the risk of abnormal pregnancies and various forms of birth defect also rise to serious levels.
This shift is so constant and so clear that throughout history age and infertility have been seen as inseparable.
From sacred scripture to folk lore, an old woman conceives only under the most extraordinary or miraculous circumstances.
Only in the present age is that link being challenged, in ways that are allowing women who would otherwise fail to bring children to term to begin new families in their later years.
The new medical technologies that are raising the bar with regards to age and fertility range from the simple to the dramatically radical.
The array of therapies includes efforts to stimulate and harvest any remaining viable eggs a woman may have in her ovaries, followed by in vitro fertilization of those eggs.
Another method involves accepting viable eggs from a donor and then ensuring implantation of fertilized eggs and full-term pregnancy through hormone treatments.
The results, while still too few to have a serious impact on the normal age-associated infertility statistics of a nation, much less the world, are increasingly allowing growing numbers of women to give birth to healthy, normal children who would have been no more than a dream as little as a decade ago.
Fertility in men also decreases with age, though the effect is not as pronounced as it is with women.
A man's increasing age brings with it a drop in the production of fully mature sperm.
The volume of sperm remains fairly constant, however, the quality and "ripeness" of the sperm declines.
Immature sperm are less motile, thus less likely to ever reach an available egg.
There is also an increased level of genetic damage in the sperm of older men, which can lead to a greater number of failed conceptions and pregnancies, even if fertilization should occur.
Therapies for men suffering from age-related fertility issues include treatments to increase the production of healthy sperm, and a range of sperm harvesting methods that reserve the highest quality sperm to be combined with a healthy egg.
This increases the chances of a successful pregnancy.
Infertility statistics improve in the face of direct therapy, and while there are no certainties, treatment is likely to increase the odds of a positive outcome.
In times past, older couples couldn't do much more than hope and pray for a miracle child.
Now there are tangible steps they can take to help the miracle of conception and birth along its path.
Age and infertility are no longer inescapably linked.
By consulting a professional infertility specialist both men and women can uncover the state of their own fertility, and take action to accomplish outcomes previously beyond their reach.