It stands to reason that when a population delays family formation and childrearing, starting years or even decades later than in the past (say... 30+ compared to late teens), there will be dramatically fewer children born. In the case of some couples, no children at all (even if some are desired).
If you live in Europe then the population of your country 30 years from now will most likely not look much like you, and the prevailing culture, institutions, and religions will look more like those of newcomers who have higher birth rates, at least for the first couple of generations, and less like those of yours/your-parents.