Otherwise just drink to comfort. Drinking excess fluids to 'flush' your system out is a fallacy and you will just urinate more. Elevating your legs will help some but generally as soon as you stop it will return. Rest assured as long as your blood pressure behaves it will go away after delivery. And unfortunately yes, it can get worse.
Blood clots can occur during pregnancy due to the high levels of estrogen and may present as swelling and pain in a lower extremity. A Doppler ultrasound study is sometimes ordered if this problem is suspected. Swelling in association with other symptoms such as headaches or visual symptoms and elevated blood pressure may represent the clinical syndrome of preeclampsia which can have serious consequences for mother and baby. Induction of labor is sometimes performed if pre eclampsia is diagnosed.
Evaluation by your Obstetric provider is advisable to make sure these other serious problems are not present and the swelling is due to the physiologic changes of pregnancy. Regular prenatal care is necessary to make sure your blood pressure is normal and your pregnancy is progressing as it should.
If these other serious problems are not a concern, then elevation of the lower extremities and compression stockings can be helpful in alleviating symptoms.
The American College of Obstetricians and Gynecologists publishes a patient information site that can be accessed by typing ACOG FAQ into your search tool bar. PDFs on various pregnancy topics are available there.
Hope this was helpful
Dr. Chunjai Clarkson