Well, actually they were in the middle of a big crisis with the astoroid, so yeah the baby was in danger. And, as Chris said, the whole point of what Ree did was to get the baby out of danger (which was real), so there really was no way he would have allowed any kind of harm to come to her.
Good point. The ship and crew were
in imminent danger, and Ree acted to remove the baby from that danger. It was an overreaction, but the threat was real. And after that, he made a point of taking Deanna to the one world within range that was safest for the baby -- the natives were small and rarely violent, their technology was not advanced enough to pose a threat, but they were humanoid enough and had sufficient medical science that they would have adequate facilities for ensuring a safe delivery and postnatal care. Within the context of a mindset that elevated the baby's safety above all other considerations, Ree's choices were quite logical. True, as Deanna pointed out, by creating a hostage situation, Ree did generate a degree of risk, and that was where his judgment became questionable. But in his state of mind, he convinced himself that the risk was minimal, certainly in comparison to that of being on a starship on the verge of destruction.