The intense fall in births, here, and even more dramatically in Europe, is one of our greatest challenges, and one I think about a lot.
Europe is rather mixed on this topic:
There are several countries such as Sweden, Norway, Germany, Austria, Switzerland - where births increased a lot in the past 2 decades (mostly because of immigrant mothers, but not exclusively).
Also, in Poland births reached a new record level last year - because of generous child tax benefits.
Eastern and Southern Europe (excl. Poland and the Czech Republic) have seen large declines though - because of their crappy economies.
Other countries such as France, the UK, Netherlands, Ireland had upticks in the early 2010s, but births have fallen again by a bit.