Resting Heart Rate

At 36+ weeks I’d expect my resting heart rate to be higher (or at least the same) but it seems to be lowering. I don’t track it all day long, just while I sleep becuase I wear a Fitbit for a silent alarm. My resting heart rate has been around 67-69 for the most part but this week it has been a bit lower 64-66.

I know it’s not drastically different but is that normal? Anyone else notice this happening?