T.B.
First of all, you need to talk to your OB. My OB recommended I wear compression panty hose, not to be confused with regular panty hose. I wore them with my third pregnancy and now with my current pregnancy. I'm 38 weeks along and I have been wearing these compression panty hose from the beginning to prevent my veins from popping out. They come in different compressions, so many different brands, and believe me, I've tried MANY kinds until I landed on the pair I have now. They make my legs feel wonderful. Without them, my legs feel like heavy logs. And so far, none of my veins have popped out thus far.
My compression grade is 16-20. Talk to your OB about it A.S.A.P. A clot could be very serious. Also, varicose veins are painful so DO keep your legs elevated as much as possible.
Also, IF your doctor recommends compression panty hose, put them on before you even get out of bed. I keep my pair at the end of my bed and each morning before I even get up to use the bathroom, I put them on. The reason is to keep your blood from filling those veins up and plumping them before you have a chance to put the hose on. And beware, these type of hose are a challenge to put on...but very worth it in the long run.