Development of the vascular system continues until adulthood. Some blood vessel disorders are the result of the overreproduction of blood vessel cells. For example, the hemangioma, which typically appears soon after birth, goes through a period of rapid growth in which the blood vessel cells multiply excessively. Other blood vessel disorders occur from vascular malformations essentially errors in development that occur between the 4th and 10th weeks of pregnancy. Most vascular malformations, such as port-wine stains, are present at birth, although some manifest years later.
Pregnancy is a time when hormonal influences can cause blood vessel changes.
Some women develop excessive numbers of spider angiomas. These are tiny dilated blood vessels found in the skin's surface layer. Many of these blood vessels regress after pregnancy, when hormone levels return to normal. If they don't resolve, treatment is available to eradicate them. My child was born with a port-wine stain on the side of his face.