The uterus is composed of a interconnected muscle fibers known as the myometrium. The blood vessels that provide the blood supply to the placenta pass through this muscle. After labor it is the contraction of these muscles that physically squeeze the blood vessels so that hemostasis can occur after the delivery of the fetus and the placenta. Local hemostatic factors like tissue factor type-1 plasminogen activator inhibitor and platelets and clotting factors aid in stopping the blood flow. This physiological contraction does not occur if the myometrium becomes atonic. Oxytocin is released continuously during labor to stimulate uterine muscle contraction so the that the fetus can be delivered and it is continued to be released after delivery to stop blood flow. If the oxytocin receptors become desensitized and no longer respond to the hormone then the uterus does not contract. The uterus can also be structurally damaged or distended to prevent contraction. Therefore, as placenta is delivered arteries are damaged and without the muscle contractions hemostasis cannot be reached. Blood loss is an expected part of labor and less than 500 mL is considered normal. Generally, primary PPH is classified as being more than 500 mL of blood lost in the first 24 hours following delivery. Those who have a caesarean section typically have more blood loss than a vaginal birth; so 1000 mL is commonly used to determine excessive blood loss. It is easy to underestimate maternal blood loss because the primary method of assessment is visual observation.
medical cause of Postpartum bleeding
medical cause of Abnormal uterine bleeding
symptom of Postpartum infections
symptom of Postpartum bleeding
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complications of Abnormal uterine bleeding
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symptom of Eclampsia