Medically reviewed for accuracy.
Youre going about your business applying moisturizer to your legs or getting dressed.
Then you see it: Spidery purplish lines on your thighs or the back of your legs.
If you do develop spider veins, the good news is theyre mostly harmless.
What are spider veins?
Spider veins are simply swollen veins that are visible just under the surface of the skin.
Spider veins can also occur on the face or other areas of the body.Trusted SourceU.S.
First, a quick explainer of how spider veins develop in general.
Typically, the valves in veins push blood in one direction to the heart.
However, sometimes the valves can weaken and have problems closing.
If the valves dont close correctly, blood can leak back into the bottom of the veins.
Over time, the blood builds up, causing the wall of the vein to weaken and grow larger.
Thats when the spider veins or varicose veins start to appear.
What do spider veins look like?
While spider veins are visible through the skin, they dont make the skin bulge out like varicose veins.
Spider veins can occur alone or with varicose veins and visible veins.
Will spider veins that develop during pregnancy go away?
While they might be driving you crazy now, spider veins are usually a temporary side effect of pregnancy.
They typically shrink after you give birth, when your blood volume falls back to normal.
That might be within three or four months.
Sometimes, though, they may not go away completely.
While its impossible to prevent spider veins completely during pregnancy, there are ways to minimize their spread.
