I hadn't really heard of that but when I looked it up, it has a name and everything! This increased saliva is associated with nausea and vomiting. Do you have these symptoms as well. Ptyalism gravidarum is the name. https://pubmed.ncbi.nlm.nih.gov/26264544/ Talk to your doctor about it as they may be able to help you if it is going on to a level that is uncomfortable. It's generally harmless in terms of the pregnancy though.