From what I gathered, Ree's haste was due to how he couldn't set a time as to when Deanna's body would reject the fetus - it could be a month, a week, or in five minutes. He wanted to deal with it as soon as possible, since there was no crisis requiring Deanna to be in action when she should be in surgery or recovering.
Yes, I get that. But right at that moment, the pregnancy was still intact, the fetus wasn't viable, but it wasn't dead yet either. It would be different entirely, if the fetus were already dead and left in the womb, but that's not what happened - it would happen eventually, but it didn't already. At least that's what I gathered from Ree's explanations.
And quite frankly, given Ree and to a lesser extent Vale's attitude, no pregnant woman should remain on duty - because it's the nature of a pregnancy that something *could* happen at an inconvenient time... as we've already seen in Titan #1 or #2 (can't remember which now)...