Why did Lewis and Clark believe that the presence of Sacagawea's baby might have a beneficial effect on the expedition?

To Indian tribes, the presence of an infant meant that they were a peaceful party. So, if Lewis, Clark, and mother Indian were to have stopped at any tribes, the tribe would know that they were not a war party.

To Indian tribes, the presence of an infant meant that they were a peaceful party. So, if Lewis, Clark, and mother Indian were to have stopped at any tribes, the tribe would know that they were not a war party. - - - So then they would not be worried about being attacked or have to prepare for an attack