I'm not a 100% sure, but I do believe that nidoqueen is running though a menopause state.
this thing happens to elderly females and other animals. Nidoking can breed fine, however I'm not sure about Nindorina, even though chances are to a human young female is about 1% in the late 30s.
but with this kind of thing Nidoqueen, I dunno.
by the way, sorry if this question was a few years late than usual.