Bristol has reappeared, in NYC. It is not clear whether she's been traveling with the campaign all along, or where she has been. As far as I know it's been over a month since anyone else has seen her or photographed her.
Here are three still shots captured from a video.
Here is the video.
Watch carefully, right at the :15 sec. point what appears to be a bodyguard (non secret service) moves Bristol into the hotel.
From these shots it's very difficult to tell if her stage of pregnancy has advanced in the six weeks since she was photographed at the RNC. You decide.