most likely vericose veins....they CAN be common. As Diane said, the pressure from the uterus causing the veins to swell. Most women get them on their legs...but a lucky few of us get them on the vulva. These are referred to as Vulvar Vericosities. While not dangerous, they CAN be uncomfortable. Wear supportive cotton underwear. They may ache, some women complain that they hurt. Fortunately they should return to normal after birth, after the pressure is relieved. They can cause VISUAL swelling of the external genitalia and pubic mounds. There is a very very small risk that one of these veins could rupture during vaginal childbirth but the risk is so small docs don't even usually discuss it.
Vericose veins are common in pregnant women - unfortunately. There's so much pressure in that area from your weighted uterus - that this can happen. Ask about it at your next check up - and they can take a look to let you know what's going on.
dont think so its more like a varicos vein very long one at that