While you may enjoy your vegetarian diet regularly and intake enough calories and sustenance for yourself, you may not be getting the proper nutrition for your developing baby. It is definitely possible to continue your vegetarian diet, but you need to be extremely conscience of what you take in and monitor yourself closely.
Make sure that you are getting proper amounts of D vitamins by getting at least an hour of sun a week without sunblock. Go for a twenty minute walk three times a week when the sun is at its weakest (late afternoon or early morning before 11), and this way you can get in some exercise and vitamins. Protein needs up by 30% during pregnancy, so make sure to eat even more nuts than you usually do.
B-12 is extremely important for the development of your baby, so either take a multivitamin or find fortified milk or cereal. Another vitamin you need is calcium, which you can find in milk, green vegetables, and milk products- you should have at least four servings a day.
Iron supplements might also be something you might consider taking during pregnancy. Iron levels are especially important during the later half of pregnancy, and it can be found in dark green vegetables, nuts, seeds, and fortified cereals. Zinc is another supplement you might consider- it can be challenging to get the appropriate amount needed during pregnancy from only legumes and whole grains.
Other vitamins necessary for pregnancy that you need from food are things like folic acid, vitamin C, and vitamin A. Just like daily life, be sure to keep your balance, but do not diet or deplete yourself of anything during pregnancy. If you have any concerns about your diet, ask your doctor.