Changes in Hormone Balance Brings Increased Risk of Clotting

The most common cause of maternal death during pregnancy is a blood clot, with an incidence of one to five per 1,000 pregnancies, including the period immediately following childbirth. In women with a previous history of deep vein thrombosis, the risk of additional deep vein thrombosis with pregnancy is 12-35% and increases to 75% in women with inherited clotting disorders.

Causes of pregnancy-related blood clots include:


Estrogens and oral contraceptives mimic hormone levels found in the pregnant state, leading to clotting protein changes. The use of hormone therapy may, therefore, lead to an increased risk of blood clots, especially in women with clotting disorders, such as factor V Leiden.