Let's say all we can now before Kurenai approves or disapproves it. Say Hiden's curse jutsu binds to a spirit. If Kurenai has two spirits merged in one body because she is pregnant, casting her under the curse would be beyond the capacity of Hiden's curse jutsu which can only bind to one spirit at a time. Therefore, Kurenai may, to Hiden's surprise, be unaffected by Hiden's curse jutsu, and be able to revenge with her team. I also see people talking about genjutsus might be unaffected. To something as absurd as Hiden's ritual, we can't be so sure if they are the way we think it will work. What do you think... ? (edit) Can pregnancy dispell Hiden's ritual ? And go Kurenai !