Hi asaara,
Many factors increase a person's chances of developing spider veins (telangiectasia), including advancing age; a family history of vein problems; obesity, leg injury, prolonged standing and other things that weaken vein valves; sun damage; and, hormonal changes. They are associated with estrogen, which likely is why they're much more common in females. They tend to develop when estrogen levels are elevated, such as when pregnant, taking oral contraceptives and on estrogen replacement.
It is very unlikely that anything directly related to scuba either causes or makes them worse, and certainly not the transient and relatively infrequent pressure changes inherent in diving. In fact, veins most often dilate and become varicose as a result of increased downward pressure on the vein from a point above it. Scuba would be expected to decrease rather than produce such pressure.
While they can be unsightly, spider veins usually are not harmful or painful and do not need medical treatment. But, in some cases they may cause discomfort, become excessively dense or bleed, and if so evaluation should be sought.
Helpful?
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.
Regards,
DocVikingo