Negan's Fertility?

I have a question...Has Negan spawned any kids from his "harem"?  Were there any in the comics?  It seemed to be an issue early in S7 when Sherry was getting a pregnancy test, and everyone seemed a bit upset that she was NOT pregnant!  So he has had all these women to have sex with, and seems no kids......well?
What's up with that? 

Is he shooting blanks, or what?