Placenta previa

Introduction The normal attachment of the placenta is at the posterior, anterior or side wall of the uterine body. If the placenta is attached to the lower uterus or over the cervix, the position is lower than the exposed part of the fetus, called the placenta previa. Placenta previa is one of the main causes of late pregnancy bleeding, which is a serious complication during pregnancy. Improper treatment can endanger the safety of mother and child. More common in maternal, especially multi-partum women. In the third trimester of pregnancy, the painless recurrent vaginal bleeding is the main symptom of the placenta previa. Occasionally occurs in the 20th week of pregnancy.

Cause

It is not clear at present and may be related to the following factors.

1. Endometrial lesions of the uterus: such as puerperal infection, prolificacy, multiple curettage and cesarean section, etc., causing endometritis or endometrial damage, causing uterine decidual blood vessels to grow incomplete, when fertilized eggs At the time of entry, the blood supply is insufficient, and the placenta area is enlarged in order to take sufficient nutrition to extend to the lower part of the uterus.

2. Abnormal placenta: such as the para-placenta, the main placenta in the body of the uterus, and the placenta to the lower part of the uterus near the cervix.

3. Fertility egg trophoblast developmental delay: When the fertilized egg reaches the uterine cavity, it has not yet developed to the stage of implantation, and continues to transplant into the lower uterus, where it grows to form the placenta previa.

an examination

Related inspection

Obstetric B-ultrasound palpation

1. History: Painless vaginal bleeding without predisposition in the third trimester or at the time of labor should be considered as the placenta previa. If the bleeding is early and the amount is large, the possibility of complete placenta previa is large.

2. Signs: According to the amount of blood loss, multiple bleeding, showing anemia, acute massive bleeding, can occur shock. Except for the first exposure of the fetus, the abdominal examination is the same as normal pregnancy. Excessive blood loss can occur in the fetal intrauterine hypoxia, severe cases of fetal death. Placental murmurs can sometimes be heard above the pubic symphysis, but are not heard when the placenta is attached to the posterior wall of the lower uterine segment.

3. Vaginal examination: Generally only for vaginal peeping and sacral percussion, should not be diagnosed in the neck tube, so as not to cause the placenta attached to the place to cause large bleeding. If it is a complete placenta previa, it is even life-threatening. A vaginal examination is used to confirm the diagnosis and determine the mode of delivery before termination of pregnancy. It must be carried out under conditions of infusion, blood transfusion and surgery. If the diagnosis is clear or excessive bleeding, no vaginal examination should be performed. In recent years, B-mode ultrasound has been widely used, and vaginal examinations have rarely been done.

4. Postpartum examination of placenta and membrane: For patients with prenatal bleeding, the placenta should be carefully examined after delivery to verify the diagnosis. The placenta in the front part has black and purple old blood clots attached. If the distance between the membrane and the edge of the placenta is <7cm, it is a partial placenta previa.

Differential diagnosis

Placenta previa should be differentiated from placental abruption:

Placental abruption: After 20 weeks of gestation or during childbirth, the placenta in the normal position is partially or completely detached from the uterine wall before the delivery of the fetus, called placental abruption. Placental abruption is a serious complication in the third trimester of pregnancy. It has an acute onset and rapid progress. If it is not treated in time, it can endanger the mother and child. The incidence of domestic reports is 4.6 to 21 , and the incidence rate abroad is 5.1 to 23.3 . The incidence is related to whether the placenta is carefully examined after delivery. Some patients with mild placental abruption can have no obvious symptoms before labor. Only when the placenta is examined after delivery, it is found that there is clot blockage in the early exfoliation. Such patients are easily overlooked.

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