At least here in the real world people have the right to refuse treatment also if it endangers his or her life or is even fatal. This is certainly the case when such a person is able to make such a decision. Deanna is of course under a lot of strain. So far I have read two third of Mere Mortals but never had the impression that Deanna is insane or otherwise mentally unfit.
I think people tend to forget that pregnancies can be dangerous and that in countries with poor health service a lot of mothers and babies don`t survive pregnancies and births. Many women form a very strong bond with their unborn children from early on. I certainly did and that included accepting the risks involved. If my daughter and me would not have been so lucky with having access to modern hospital care, the outcome would have been very different.
I am amazed and I admit it, also shocked about how Deanna has been treated so far. That a Starfleet doctor has the right to abort her baby against her will is not something I would have expected to read in a Star Trek book. Dr. Ree also did very little to help. I appreciate it that people of his species don`t form strong bonds with their unhatched young but to just dismiss the unborn child by saying I can`t help is the wrong attitude. He even recommended a hysterectomy! Maybe he can`t help but there are others who maybe could. Also in the real world, if a doctor lacks the specialist knowledge, he would send the patient to someone who might have the answers. Dr. Ree didn`t even try to contact someone else.
Yes, with Caeliar technology, a lot could be possible. At least such options should be discussed thoroughly before any decision is made and this decision should be Deanna`s. That means, if it comes to the worst and the fetus has to be removed it should not just be treated as a diseased, dangerous growth in her body. Maybe it is possible to remove it, keep it alive and make a decision then.