Pregnancy is the most common cause of vulvar varicosities. A 2017 study estimates that 1822 percent of all pregnant women and 2234 percent of women who have varicose veins near their pelvis develop vulvar varicosities.

An estimated 4 percent of women have had vulvar varicosities. They typically occur during pregnancy and usually go away on their own within 6 weeks after giving birth.

Vulvar varicosities are unusual in women who have not been pregnant. Although, sometimes, they occur in older women, particularly after standing for a prolonged period. Women who have varicose veins elsewhere on their body may also develop vulvar varicosities.

Every vein in a person's body has a valve that prevents blood from flowing backward. Veins in the lower body have to work very hard to carry blood back up to the heart.

During pregnancy, increased blood flow to the genitals and pressure on the lower body can make it more difficult for blood to flow in the proper direction. This may allow the blood to flow backward, creating varicose veins.

Also, during pregnancy a person's veins may dilate due to hormonal changes or pressure being placed on a major vein called the inferior vena cava, causing varicose veins.

Varicose veins tend to run in families, so women with close family members that have them may also develop them.

Rare causes include pelvic tumors that limit veins from draining.