I think Doris's point is that the term comes from the contrast between boom and bust cycles, originally in the economy but here with regard to the birth rate. It wasn't clear from meep's posts that he or she understood that, and 'drought' really isn't very close.
I think meep's point with 'break' was that 'baby buster' can be understood syntactically like 'union buster,' 'strike buster,' 'Ghostbuster,' 'clot-busting drug,' etc.; can you bust a baby?
I'm not sure a hyphen would solve that problem, because you still wouldn't read the word as [baby bust] [-er]. But I wouldn't have anything against offering hyphenated spellings as a second choice.
Pillenknick is interesting, I must have missed those previous discussions, so thanks for finding them again. It's clearly an option in some contexts, though it would probably be better not to list it as the only option in LEO, because the term 'baby bust' per se doesn't actually refer to the pill.
The main thing is to be sure that all the noun forms are in there, both for the phenomenon and the people who belong to it, but in the singular, not the plural.
So is there a word such as Pillenknicker or Generation-Xer, or do you have to say something like Mitglied der Pillenknick-Generation / der Generation X?