Why Does Blood Clotting Increases During Pregnancy?

During pregnancy, the blood clotting capacity of the body increases to a certain extent. It generally occurs as a precautionary measure to prevent excessive bleeding during childbirth. The amount of protein that is responsible for clotting of blood increases in comparison to the protein that prevents clotting. 

Problems associated with the increased tendency of blood clotting:

  • Recurrent miscarriages - A condition known as APLA (Anti Phospholipid antibody syndrome), is associated with recurrent miscarriages. Minute - minute clots are formed in small blood vessels supplying nutrition to developing an embryo. As a result, the blood supply to embryo decreases, ultimately leading to abortion. If this condition is timely diagnosed and treatment is started early during pregnancy, then such a mishap can be prevented.
  •  Preterm Delivery – APLA is also associated with preterm delivery, abruption, premature baby or rarely intrauterine demise of the baby. Premature babies are in turn prone to many other complications in breathing, vision etc. 
  • Deep Vein Thrombosis which is abbreviated as DVT is the medical condition characterized by the formation of a blood clot within a deep-seated vein of a woman, most commonly legs. Developing a clot during pregnancy can be quite serious and if left untreated can further lead to life-threatening complications. Besides increased clotting tendency during pregnancy, there are several other causes that contribute to Deep Vein Thrombosis such as enlargement of the uterus which tends to create more pressure on the veins thus resulting in a blood clot. 

Risk Factors:

There are several factors that tend to increase the risk of clotting and developing deep vein thrombosis during pregnancy. Common factors include age i.e. if you are 35 years or older during your pregnancy, the chances of Deep Vein Thrombosis increases considerably. Other factors include hypertension or pre-eclampsia, severe varicose veins, a family history of deep vein thrombosis, smoking or if you have a C-section surgery.


The symptoms of deep vein thrombosis are usually observed in one leg. The symptoms are basically characterized by a sharp pain in the leg which does not go away, softness and tenderness in the thigh or the calf and inflammation in the leg. Sometimes the blood clot in the leg can move upwards towards our lungs and can form a blood clot there. Symptoms of this particular condition include blood in the mucus when you a cough, difficulty in breathing, chest pain and a rapid heart rate.

In case, a woman has 2 or more abortions or any premature delivery associated with abruption, then she should undergo blood tests for diagnosing APLA. Once it is confirmed then she needs to be started on blood thinning medicines and injections, whenever she becomes pregnant. The chances of successful pregnancy increase dramatically from 20% (without treatment) to 80%(with treatment).


There are a lot of ways to prevent the development of deep vein thrombosis during pregnancy. The common preventive measures include several pregnancy exercises to maintain blood flow throughout the body and walking and stretching at regular intervals. The primary aim is to maintain proper blood flow and regular circulation throughout the body.