Swallow. Excess saliva is not necessarily a bad thing. Saliva is very important because it contains digestive enzymes that start the digestive process, it cleanses and rinses the mouth, and buffers the acidic ph of acidic food/beverages and acidic dental plaque. Thank your lucky stars you have plenty of saliva. Alternatively, dry mouth leads to rampant dental decay if not managed properly.
Not much. Excessive salivation in pregnancy is called ptyalism. Some women especially in early pregnancy will over produce saliva and feel nauseated when they swallow it. Many will end of carrying around a spit cup. There are no real treatments for this. Chewing gum or sucking on candy can help distract you.
Saliva. Your saliva is yours and of course is not going to hurt but help you. Salivation is usually promoted by chewing (such as gum) or sight, smell, taste, or even thought of food. Very unlikely but it can be induced by a tumor of the salivary gland but that would be unilateral. If concerned see a dentist or physician for further consult. It won't hurt to just keep swallowing it as well.