Pronounced cress-TSEN-tsee-ah in German. Short froms are Kreszenz and Zenzi. There are two Catholic saints by that name, martyr Saint Crescentia (died about 304 AD) and Saint Maria Crescentia Höss (1682-1744). An alternative spelling is Kreszentia, for example German politician Kreszentia Flauger (born 1966). It used to be quite popular in Catholic areas due to the saints, but it is rarely given to babies these days. Personally, I think it's a bit too much and prefer the shorter from Kreszenz.
I bear this name (in fact I am that politician above) and I live in Germany. The name is more prevalent in southern Germany, especially Bavaria, than in the north where it is extremely rare. Though I am named with the German version Kreszentia I personally like the English / Latin version Crescentia better, maybe due to having learned Latin at school. It sure is an interesting, unusual and beautiful name.