What is the role of tissue 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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Uterine contraction and retraction leads to detachment and expulsion of the placenta. Complete detachment and expulsion of the placenta permits continued retraction and optimal occlusion of blood vessels.

Retention of a portion of the placenta is more common if the placenta has developed with a succenturiate or accessory lobe. Following delivery of the placenta and when minimal bleeding is present, the placenta should be inspected for evidence of fetal vessels coursing to the placental edge and abruptly ending at a tear in the membranes. Such a finding suggests a retained succenturiate lobe.

The placenta is more likely to be retained at extreme preterm gestations (especially < 24 wk), and significant bleeding can occur. This should be a consideration in all deliveries at very early gestations, whether they are spontaneous or induced. Recent trials suggest that the use of misoprostol for second trimester termination of pregnancy leads to a marked reduction in the rate of retained placenta when compared to techniques using the intrauterine instillation of prostaglandin or hypertonic saline. [16] One such trial reported rates of retained placenta requiring D&C of 3.4% with oral misoprostol compared to 22.4% using intra-amniotic prostaglandin (p=0.002). [17]

Failure of complete separation of the placenta occurs in placenta accreta and its variants. In this condition, the placenta has invaded beyond the normal cleavage plane and is abnormally adherent. Significant bleeding from the area where normal attachment (and now detachment) has occurred may mark partial accreta. Complete accreta in which the entire surface of the placenta is abnormally attached, or more severe invasion (placenta increta or percreta), may not initially cause severe bleeding, but it may develop as more aggressive efforts are made to remove the placenta. This condition should be considered possible whenever the placenta is implanted over a previous uterine scar, especially if associated with placenta previa.

All patients with placenta previa should be informed of the risk of severe PPH, including the possible need for transfusion and hysterectomy.

Finally, retained blood may cause uterine distension and prevent effective contraction.

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