1. There is no harm due to an occasional, accidental swallowing of chewing gum. The swallowed chewing gum will pass through indigested. A small amount of chewing gum is not likely to cause any obstruction anywhere in the gut of an adult.
2. Swallowing is a complex process and it is difficult for everyone to swallow while lying down on one side. In this position it is difficult for the epiglottis
to guide the food bolus through the pyriform fossa and away from the larynx
and windpipe). If you also turn your head to one side while lying down on your side, it makes swallowing even more difficult.