Theres also a significant increase in the blood volume during pregnancy, which tends to distend veins, causing valve dysfunction which leads to blood pooling in the veins. Moreover, later in pregnancy, the enlarged uterus can compress veins, causing higher vein pressure leading to dilated veins. Varicose veins that form during pregnancy may spontaneously improve or even disappear a few months after delivery. Life-style/occupation: Those who are involved with prolonged sitting or standing in their daily activities have an increased risk of developing varicose veins. The weight of the blood continuously pressing against the closed valves causes them to fail, leading to vein distention. Other acquired causes
Acquired telangiectasia, not related to other venous abnormalities, for example on the face and trunk, can be caused by factors such as

Cushings syndrome
Rosacea
Blepharitis
Environmental damage such as that caused by sun or cold exposure
Age
Trauma to skin such as contusions or surgical incisions. Radiation exposure such as that experienced during radiotherapy for the treatment of cancer, e.g., radiation proctitis
Chemotherapy
Carcinoid syndrome
Limited systemic sclerosis/scleroderma (a scleroderma sub-type)
Chronic treatment with topical corticosteroids may lead to telangiectasia. Spider angiomas are a radial array of tiny arterioles that commonly occur in pregnant women and in patients with hepatic cirrhosis and are associated with palmar erythema. In men, they are related to high estrogen levels secondary to liver disease. Tempi syndrome
Tobacco smoking
Cutaneous collagenous vasculopathy

Treatment
Before any treatment of leg telangectasia (spider veins) is considered, it is essential to have duplex ultrasonography, the test that has replaced Doppler ultrasound.
Telangiectasias, also known as spider veins, are small dilated blood vessels that can occur near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. These dilated blood vessels can develop anywhere on the body, but are commonly seen on the face around the nose, cheeks and chin. Dilated blood vessels can also develop on the legs, although when they occur on the legs, they often have underlying venous reflux or "hidden varicose veins" (see Venous hypertension section below). When found on the legs, they are found specifically on the upper thigh, below the knee joint and around the ankles. Many patients with spider veins seek the assistance of physicians who specialize in vein care or peripheral vascular disease. These physicians are called vascular surgeons or phlebologists. More recently, interventional radiologists have started treating venous problems. Some telangiectasias are due to developmental abnormalities that can closely mimic the behaviour of benign vascular neoplasms. They may be composed of abnormal aggregations of arterioles, capillaries or venules. Because telangiectasias are vascular lesions, they blanch when tested with diascopy. Telangiectasias, aside from presenting in many other conditions, are one of the features of the acronymically named CREST syndrome, a form of systemic scleroderma. The syndrome recognises the significantly co-presenting symptoms of calcinosis, Raynauds phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia. Causes
The causes of telangiectasia can be divided into congenital and acquired factors. Genetic
Goldman states that "numerous inherited or congenital conditions display cutaneous telangiectasia".