Fertility is the area where people are most often frightened and least often informed. Both the panic and the reassurance tend to be overstated.
What is broadly true
Fertility declines with age, gradually through the thirties and more steeply after forty. That decline is real, gradual, and highly variable between individuals. Population statistics describe populations; they do not describe you.
What is often overstated
Widely circulated figures about a sharp cliff at a particular birthday come largely from historical data that predates modern medicine. The direction is right. The precision is not.
What is often understated
How long the process takes. Finding the right person, having the conversations properly, taking legal advice, and then conceiving is not a matter of weeks. Several cycles is normal even where everything is fine. Building that into your planning is more useful than any statistic.
Testing
AMH and antral follicle count give an indication of ovarian reserve. They are informative and frequently over-interpreted: they say something about quantity, little about quality, and are not a prediction. Useful for planning, not for despair.
The practical conclusion
If you are thinking about this, start the conversations now. Not because there is a deadline next year, but because the parts that take longest — finding the right match and getting the arrangement right — are the parts you cannot compress. The medical timeline is usually not the binding constraint. The human one is.