During pregnancy, the weight of your developing baby can put pressure on the blood vessels in your pelvis. This causes blood to back up into the veins of the legs, enlarging them.
Wearing support hose as well as getting regular exercise can help minimize the risk for developing varicose veins during pregnancy, says Macrene Alexiades, M.D., a dermatologist and assistant clinical professor at Yale University of Medicine.
After delivery and once you finish breastfeeding, small spider veins can be treated by a dermatologist with a laser or injection procedure. For larger varicose veins, seek out a vascular surgeon.