Female sex hormones are a major cause of varicose veins during pregnancy. While a woman is pregnant the body will undergo a great deal of change. Hormone levels change and this can result in changes to the body including the increase in the amount of progesterone.
An increase in progesterone can cause blood vessels to relax which can lead to swelling of the veins. In addition to this, female sex hormones can directly cause spider veins, thread veins and broken veins.
If you have a history of varicose veins in the family, you are more likely to develop them as well. Varicose veins also tend to get worse with each pregnancy so if a patient experiences them during their first pregnancy then it is more likely that they will experience them in increasing strength in subsequent pregnancies.
The increased blood in the body during pregnancy places extra burden on veins. As the uterus grows it also creates pressure on the major veins in the pelvic area. This pressure, in turn, adds more pressure to the large vein on the right side of the body called the inferior vena cava. This can all push onto the leg veins and may result in varicose veins.