I found this series when an author mentioned it in her acknowledgements. I dove in and didn’t return until I’d read all three.
Even after three books, my brain replaced the women — the senate, the warriors, the wealthy and powerful — with men. Pausing mentally to switch them back was worth every second. (But the books are worth reading regardless.)
Scorpica
by G.R. Macallister
The second book of The Five Queendoms series.
Five hundred years of peace between queendoms shatters when girls inexplicably stop being born. A cascade of political and personal consequences expands across all five queendoms. A warrior queen must rise from childbirth bed to fight for her life. A healer in hiding is desperate to protect the secret of her daughter’s explosive power. A queen's desperation to retain control leads her to risk using the darkest magic. And the generation of lastborn girls must bear the hopes and traditions of their nations if the queendoms are to survive.