Yes, because the extra weight gain can cause achy legs during pregnancy. It is normal for the body to retain fluids because of hormonal changes causing swelling. The extra weight puts pressure on veins preventing fluids from flowing as they should. Getting plenty of rest and propping the feet and legs up might help the aching.
This could be a sign of dehydration, which is common in the first trimester. I would make sure that you are well hydrated for several days in a row and if it continues contact your doctor.
I have read a lot about pregnancy researching this movie that I was writing over the summer. It is normal for pregnant women to have achy legs at night in early pregnancy. Check out the book 'What to Expect When Expected' for lots of info about pregnancy.