It is not uncommon to notice prominent veins during pregnancy, especially around the 20-week mark. The increased blood volume and hormonal changes can cause the veins to become more visible. This phenomenon is known as "vascularity" or "vasodilation." The blue color is due to the deoxygenated blood returning to the heart. While it may be alarming to see these veins stand out so much, they are usually harmless and will likely fade after childbirth. However, if you experience pain, swelling, or any other concerning symptoms along with the visible veins, it's best to consult your healthcare provider for further evaluation.