Postpartum Bleeding and Blood Clots

During the postpartum period, roughly the six weeks following giving birth, women can be affected both by bleeding disorders and blood clotting. Also known as post-partum hemorrhage, the term post-partum bleeding generally refers to excessive bleeding during the first day after birth, but serious bleeding also can occur during the several weeks following delivery. Factors that put you at risk for developing postpartum bleeding can be grouped into two broad categories: pregnancy complications and bleeding disorders occurring independently of pregnancy.

Pregnancy complications that can cause postpartum hemorrhage include abruptio placentae (placental abruption; the placenta detaches prematurely from the uterus), placenta previa (the placenta blocks the birth canal), an overdistended uterus, multiple pregnancy (twins, triplets, etc), preeclampsia, many previous births, infection, and prolonged labor.

Bleeding disorders include inherited platelet disorders, such as Glanzmann thrombasthenia and Bernard-Soulier syndrome, both of which are fairly rare, plus a very common condition (the most common bleeding disorder) known as von Willebrand disease (vWD), which is a problem of both platelets and the inner lining of blood vessels. While women with vWD may actually improve during pregnancy, the biochemical changes in the blood that cause this improvement tend to subside at the end of pregnancy, which can put a woman at risk of post-partum hermorrhage. Treatment of vWD may consist of a particular clotting factor, platelets, or a hormone called desmopressin, depending on the severity and characteristics of the particular case.

Hemophilia is another inherited bleeding condition. While the most common types of hemophilia (types A and B) are rare in females, a third type, called hemophilia C, strikes females as much as males. Sometimes called Jewish hemophilia, hemophilia C occurs in Ashkenazi Jews more than in any other group and the main treatment is called tranexamic acid, given to prepare you for labor and delivery. If you are taking tranexamic acid, you should know that there is some concern about it getting into breast milk, but the concern is fairly low. Studies show that only small amounts will get into your milk, so if you really need this agent, most doctors will not use it as a reason for you to avoid breastfeeding.

Thrombosis is the medical word for a blood clot that occurs within a blood vessel, preventing blood from moving through the vessel. Clots can develop in arteries or veins, but venous thrombosis (clots in veins) are the main concern when it comes to clotting in young, healthy women. Venous thrombosis is caused by problems with what’s called the coagulation system (opposite the problems that cause hemorrhage) together with a tendency of venous blood to slow down and stagnate during and just after pregnancy, especially in the deep veins. The principal deep venous clotting problems during the post-partum period are deep venous thrombosis (DVT) and central vein thrombosis (CVT). Both DVT and CVT can obstruct blood flow severely.

Doctors can use a range of procedures for diagnosing venous thrombosis. One diagnostic technique for diagnosing DVT is called compression ultrasound (CUS).  It is painless and noninvasive. For diagnosing CVT, the best technique is called time-of-flight magnetic resonance venography (TOF-MRV).

If a venous thrombosis is not discovered and treated, the clot, or a piece of the clot can break off, and become a traveling clot, called an embolus. Emboli are extremely dangerous, because they can get stuck in different locations throughout the body, causing an embolism, a clot resulting from an embolus and obstructing a blood vessel. A pulmonary embolism, an embolism in the lung, is an example of such a danger. Since virtually all of the blood passes through the lungs, a pulmonary embolism is potentially fatal if it is not recognized and treated early. Usually, the prospect of a pulmonary embolism is the biggest concern in women who suffer a DVT or a CVT, because an embolus generated in a deep or central vein will be carried through the right side of the heart to the lungs, where the embolus will get trapped. In some people, however, blood and anything carried in the blood, can pass from the right side of the heart directly to the left side of the heart without going through the lungs. This can be a result of a failure of the foramen ovale –an opening between the right and left atria (upper heart chambers) during fetal life– to close after birth. Known as a patent foremen ovale (PFO), the condition can be present all the time, but in many cases the foramen ovale opens only in a particular circumstance when the pressure on the right side of the heart increases substantially compared with the pressure on the left side of the heart. In any event, an embolus that bypasses the lungs and goes directly to the left side of the heart can get into the arteries that supply the heart itself (coronary embolism), or into the brain (cerebral embolism). As with a pulmonary embolism, the situation is extremely dangerous.

Doctors must observe pregnant women who may have venous thrombosis in order to look for signs of pulmonary embolism and other dangerous complications. A major sign of pulmonary embolism is difficulty with breathing. One way to check for pulmonary embolism by way of a ventilation/perfusion (V/Q) scan. This procedure analyzes the flow of air using a radioactive substance. Another method for diagnosing pulmonary embolism is called computer tomographic pulmonary angiography (CT-PA). Some chest specialists opt for using simple flat X-ray scans instead of CT-PA in order to reduce amount of radiation to which the fetus is exposed, but this is a highly controversial choice, because CT-PA is a much better test for detecting pulmonary embolism, a condition that can kill the woman and her fetus, if not detected and treated immediately.

To treat venous thrombosis, the strategy is to dissolve the clot, and also to lower the tendency for the woman’s blood to clot by modifying the coagulation system. Physicians do this with an agent called heparin, which binds to an anti-clotting factor called anti-thrombin. In binding, heparin helps anti-thrombin work better so it takes longer for clots to form, leading clots to break up. Different types of heparin are available. For pregnant women, the choice is called low molecular weight heparin (LMWH). When no LMWH is available, your doctor would choose a type of heparin called unfractionated heparin (UFH).

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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