What is the role of lab tests in the workup 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 antenatal period, a CBC is performed. Findings alert caregivers to women with anemia and indicate interventions to attempt to improve the hemoglobin level. Hemoglobin levels below 10-10.5 g/dL have been associated with adverse pregnancy outcome, and the rare patient with thrombocytopenia will be identified. [29] Women admitted to labor and delivery units should have a CBC performed if one has not been performed recently. All women experiencing antepartum bleeding should have a CBC.

Blood typing and antibody screening tests may also have been performed in the antenatal period. If the results are known and no blood group antibodies were present, then the test may not need to be repeated upon admission. However, many facilities routinely repeat this test (or at least draw a sample to be held in the blood bank) in case blood is urgently needed. The time frame between a request for blood products of various types and their availability should be known. In a patient at high risk of PPH, crossmatching of 2-6 U of blood before delivery is prudent. Examples include previous severe PPH, placenta previa, possible placenta accreta, multiple previous cesarean deliveries, known coagulation disorders, or severe thrombocytopenia. The American Association of Blood Banks currently recommends retesting women at high risk every 72 hours for the development of antibodies.

Coagulation studies are no longer routinely performed in pregnant women, including those about to undergo cesarean delivery. Instead, history is relied on to uncover previous episodes suggesting preexisting disorders of hemostasis.

  • Once the diagnosis of PPH has been made, a CBC and baseline coagulation studies should be performed.

  • Initially, the hemoglobin value does not reflect the amount of blood loss.

  • A crossmatch for 4-6 U of PRBCs should be requested and consideration given to notifying the blood bank of the possible need for additional blood products in short order.

  • Initial coagulation study findings are usually within reference ranges; however, abnormalities may be noted. This is most common when PPH is preceded by abruptio placenta, HELLP syndrome, fatty liver of pregnancy, intrauterine fetal demise, embolic events, or septicemia.

If the international normalized ratio and/or activated partial thromboplastin time are elevated, the use of fibrinogen, a thrombin time measurement, D-dimers, and a blood film should be considered. In late pregnancy, fibrinogen levels are 2-3 times the upper reference range limit in the nonpregnant state, and a level within the nonpregnant reference range should be viewed with caution if the clinical picture suggests coagulopathy.

The onset of PPH is generally rapid. With proper diagnosis and treatment, resolution usually occurs before further laboratory work or imaging can be undertaken. In experienced hands, bedside ultrasound may help reveal clots or retained products; however, the treatment of PPH includes manual exploration if bleeding persists. This renders ultrasound redundant in the acute setting at a time when treatment must not be delayed. Antenatal ultrasound is indispensable for detecting high-risk patients with predisposing factors for PPH, such as placenta previa, and is becoming increasingly sensitive and specific in the diagnosis of placenta accreta and its variants. Pelvic vessel angiography is discussed in Treatment.

PPH usually manifests with such rapidity that diagnostic procedures are almost entirely limited to a physical examination of the involved structures.

Assessment of uterine tone and size is accomplished using a hand resting on the fundus and palpating the anterior wall of the uterus. The presence of a boggy uterus with either heavy vaginal bleeding or increasing uterine size establishes the diagnosis of uterine atony. The presence of uterine atony and resulting hemorrhage usually prevents the diagnosis of PPH from other causes because of an inability to visualize other sites. For this reason, and because of the rapidity of blood loss secondary to atony, management and control of atony is paramount.

If the placenta has been delivered, inspection findings suggest whether portions of it have been retained. If it is undelivered or if retained clots or placental fragments are distending the uterus and bleeding is persisting despite appropriate ongoing treatment, manual exploration and removal should be undertaken. This is simultaneously therapeutic by emptying the uterus and permitting contraction while also aiding in the diagnosis of placenta accreta and uterine rupture. Cervical and vaginal lacerations may also be palpated at this time.

If uterine atony has been controlled and bleeding from the uterus is minimal, careful inspection of the lower genital tract reveals bleeding sites in this area. Palpation and inspection may also reveal hematomas that require treatment. The cervix and vagina should be completely visualized following all operative vaginal deliveries.

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