You’re stating a conclusion here, but you’re skipping the argument. People who disagree with you have perfectly valid concerns. Your conclusion might be correct (for the sake of argument) but you provided 0 support for your conclusion. So I think your comment is content-free, or at the very least contributes 0 to the conversation.
Maybe the most important is you don't want prisoners getting pregnant.
All women in prison are at risk of sexual violence. That comes from other prisoners (including cis women), and from officers.
Focussing attention on the small number of trans prisoners, and ignoring the risk from cis prisoners and from staff, means that women will continue to be at risk of sexual violence.
Yes but females are also subjected to sexual violence from males.