The end doesn't justify the means. Ree should have suggested that diagnostic thing and the stasis right from the start just to offer Deanna options. His two options were abortion or/and (preferably) a hysterectomy. I doubt he'd have had qualms about violating Deanna's rights as a patient - going behind her back is shady enough behaviour in such a situation.
But look at it from his perspective. His priority is the health of the patient. The stasis/monitor solution was considerably less safe for Deanna than a controlled termination of the pregnancy would have been, and there was no medical benefit to it either for the mother or the child. At best, it was just a way of delaying the inescapable reality that the fetus would die. I don't see why it's surprising that a doctor would strongly urge the safer option and be reluctant to suggest a more dangerous and completely pointless alternative. His job is to look out for the best medical interests of his patient, and if her preferences go directly against her own medical interests, then it's his medical duty to do everything he can to talk her out of it. Indeed, it would've been unethical for Ree to recommend a procedure that he knew was unsafe and medically unnecessary.
Have you seen the House
episode "Three Stories"? I don't want to spoil it, but the medical dilemma there is very similar to this, in that it involves a patient who's irrationally determined to take the most dangerous possible option against all advice from his doctor.