What is the role of thrombosis in the etiology of postpartum hemorrhage (PPH)?

Updated: Jun 27, 2018
  • Author: John R Smith, MD, FACOG, FRCSC; Chief Editor: Ronald M Ramus, MD  more...
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In the immediate postpartum period, disorders of the coagulation system and platelets do not usually result in excessive bleeding; this emphasizes the efficiency of uterine contraction and retraction for preventing hemorrhage. [5] Fibrin deposition over the placental site and clots within supplying vessels play a significant role in the hours and days following delivery, and abnormalities in these areas can lead to late PPH or exacerbate bleeding from other causes, most notably, trauma.

Abnormalities may be preexistent or acquired. Thrombocytopenia may be related to preexisting disease, such as idiopathic thrombocytopenic purpura, or acquired secondary to HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), abruptio placentae, disseminated intravascular coagulation (DIC), or sepsis. Rarely, functional abnormalities of platelets may also occur. Most of these are preexisting, although sometimes previously undiagnosed.

Preexisting abnormalities of the clotting system, such as familial hypofibrinogenemia and von Willebrand disease, may occur and should be considered. An expert panel recently issued guidelines to aid in the diagnosis and management of women with such conditions. [18] An underlying bleeding disorder should be considered in a woman with any of the following: menorrhagia since menarche, family history of bleeding disorders, personal history of notable bruising without known injury, bleeding from the oral cavity or GI tract without obvious lesion, or epistaxis of longer than 10 minutes duration (possibly requiring packing or cautery). If a bleeding disorder is suspected, consultation is suggested.

Acquired abnormalities are more commonly problematic. DIC related to abruptio placentae, HELLP syndrome, intrauterine fetal demise, amniotic fluid embolism, and sepsis may occur. Fibrinogen levels are markedly elevated during pregnancy, and a fibrinogen level that would be in the reference range in the nonpregnant state should be viewed with suspicion in the aforementioned clinical scenarios.

Finally, dilutional coagulopathy may occur following massive PPH and resuscitation with crystalloid and packed red blood cells (PRBCs).

Risk factors and associated conditions for PPH are listed above; however, a large number of women experiencing PPH have no risk factors. Different etiologies may have common risk factors, and this is especially true of uterine atony and trauma of the lower genital tract. PPH usually has a single cause, but more than one cause is also possible, most likely following a prolonged labor that ultimately ends in an operative vaginal birth.

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