What is Placenta Previa?

After 28 weeks of gestation, the placenta is attached to the lower part of the uterus, and even the lower edge of the placenta reaches or covers the inner cervix, which is lower than the exposed placenta. It is called placenta previa. Placenta previa is one of the main causes of bleeding in late pregnancy and a serious complication during pregnancy. More common in menstrual women, especially multi-maternal. According to the relationship between the placenta and the cervix, the placenta previa is divided into three types: complete placenta or central placenta: the cervix is completely covered with placental tissue; part of the placenta previa: inside the cervix The part of the mouth is covered by placental tissue; marginal placenta previa: the placenta is attached to the lower part of the uterus, reaching the edge of the inner cervix, and not beyond the inner cervix.

Basic Information

English name: placenta previa
Visiting department: Obstetrics and Gynecology

Common causes: Related to multiple pregnancy, multiple pregnancy, smoking, etc.
Common symptoms: Repeated bleeding without inducement and painless vaginal bleeding

Causes of placenta previa

The reasons are not clear at present, and are often related to the following factors:

1. Multiple pregnancy, multiple abortions, multiple uterine curets, and cesarean sections can cause endometrial damage. When fertilized eggs are implanted into the uterine decidua, due to insufficient blood supply, in order to ingest sufficient nutrition The area of the placenta is enlarged and even reaches the lower part of the uterus.

2. When the fertilized egg reaches the uterine cavity, the trophoblast is stunted and has not yet developed to the stage where it can implant, and continues to be transplanted into the lower uterus, where it grows and develops to form a placenta previa.

3. Some scholars have suggested that smoking and drugs affect the blood supply to the uterine placenta. The placenta expands its area to obtain more oxygen supply, which may cover the cervix and form the placenta previa.

4. Multiple pregnancy due to the large placental area, extending to the lower uterus and even the inner cervix.

Clinical manifestations of placenta previa

Symptoms

Inductive and painless vaginal bleeding in late pregnancy is a typical clinical manifestation of placenta previa. The cause of bleeding is that as the uterus enlarges, the placenta attached to the lower uterus and the cervix cannot stretch correspondingly, causing misplacement and separation and causing bleeding. The amount of first bleeding is usually small, and occasionally there are cases of first bleeding. As the lower segment of the uterus continues to stretch, bleeding often recurs, and the amount of bleeding increases. The occurrence of vaginal bleeding sooner or later, the number of recurrences, and the amount of bleeding have a lot to do with the type of placenta previa. Complete placenta previa usually bleeds early, about 28 weeks of gestation. Frequent bleeding occurs frequently and the volume is large. Sometimes a large amount of bleeding can make the patient fall into shock. Late, mostly in 37 to 40 weeks of pregnancy or after labor, the amount is also small; the first placental bleeding and the amount of bleeding between some of the above. In patients with partial or marginal placenta previa, the rupture of the membrane is conducive to the compression of the placenta by the fetal exposure. If the fetal exposure can be rapidly decreased after the rupture of the membrane, the placenta can be directly compressed, and the bleeding can be stopped. Due to repeated vaginal bleeding or a large number of vaginal bleeding, patients may develop anemia, the degree of anemia is proportional to the amount of bleeding, severe bleeding may occur in shock, fetal hypoxia, and even fetal death in the uterus.

2. Signs

Hemorrhagic shock such as anemia appearance, weak pulse rate increase, and blood pressure drop may occur during heavy bleeding. Abdominal examination: The size of the uterus is consistent with the menopause month. Due to the placenta covering the cervix, the fetus is exposed to the pelvis, and the fetal exposed part is very high. A placental murmur can be heard above the pubic symphysis. ^[1]

Placenta previa diagnosis

1. By asking the medical history and clinical manifestations of painless vaginal bleeding in late pregnancy, the ultrasound diagnosis of placenta in the second trimester covers the internal cervix, the physical examination is the same as above, and the basic diagnosis can be basically made. The diagnosis of placenta previa is not allowed to undergo vaginal examination or anal examination, especially the internal diagnosis of cervical canal, so as to prevent the placenta attached to the place to cause major bleeding. If a vaginal or anal finger test is necessary, it must be done carefully under infusion, blood preparation, or blood transfusion conditions.

2. Ultrasonography can clearly show the relationship between the uterine wall, fetal exposure, placenta and cervix to confirm the diagnosis.

3. Postpartum check the placenta and membrane to verify the diagnosis. The placenta in the front part has old purple clots attached to it. If the distance between the membrane break and the placental edge is less than 7cm, it is a partial placenta previa.

Differential diagnosis of placenta previa

Placental abruption

The main symptoms of mild placental abruption are bleeding from the vagina, the amount of bleeding is generally large, the color is dark red, and may be accompanied by mild abdominal pain or abdominal pain is not obvious. Severe placental abruption may occur with sudden and persistent abdominal pain and / or acid and low back pain, the degree of which varies depending on the size of the peeling surface and the amount of blood after the placenta. In severe cases, nausea, vomiting, and even pale signs, sweating, weak pulses, and decreased blood pressure can be seen. No vaginal bleeding or only a small amount of vaginal bleeding, the degree of anemia does not match the amount of external bleeding. B-mode ultrasound can detect placental thickening, post-placental hematoma, and placental position normal when placental marginal sinus ruptures.

2. Ruptured placental prevascular rupture

Mainly due to fetal bleeding, due to the abnormal position of the blood vessels, the blood vessels also ruptured when the fetal membrane ruptured. Sudden bleeding occurred, and the fetus died quickly, but the harm to the mother was not great.

3. Cervical lesions

Such as polyps, erosion, cervical cancer, etc., combined with medical history can be confirmed through vaginal examination, B-mode ultrasound examination and placenta examination after delivery. ^[2]

Placenta previa

Absolutely rest in bed, correct anemia and use antibiotics to prevent infection. If the gestational week is less than 34 weeks, restrain the contractions and give birth maturation. At the same time, observe the condition closely and conduct related auxiliary examinations. Such as repeated heavy bleeding, termination of pregnancy as appropriate.

Termination of pregnancy

(1) Caesarean section is the main method of placenta termination. Shock should be corrected before surgery, blood transfusion and blood transfusion should be used to increase blood volume. Care should be taken to choose the location of the uterine incision and try to avoid the placenta. The placenta will usually cause major hemorrhage if it is delivered to the fetus unless necessary.

(2) Vaginal delivery Vaginal delivery uses the placenta to compress the placenta to stop bleeding. This method is only applicable to marginal placenta previa with the fetus in the head position. Bleeding occurs after labor, but the amount of blood is not large, the general condition of the mother is good, and the labor process is progressing smoothly. It is estimated that the childbirth can be ended in a short time. However, it should be noted that the placenta attached to the posterior wall of the uterus is a type of placenta premature placenta that is pressed by the bony sex organs of the fetal head and the sacrum during the drop of the placenta. Oxygen, therefore requires close monitoring during labor.

2. Other

Re-pregnancy after delivery by cesarean section requires early ultrasound examination to determine the relationship between the fetal sac and the uterine incision. If it is the pregnancy of the original cesarean section incision site, you need to go to a hospital with good medical conditions to terminate the pregnancy. For pregnant women with placenta attached to the incision site in the middle and late stages, the risk of penetrating placenta implantation is high. A high-risk outpatient card needs to be established in a tertiary hospital. Early preoperative discussions and choice of surgical methods can be done according to the size of the implanted area. Use uterine massage and uterine contraction, local 8-shaped suture to stop bleeding, ligament of the uterine artery, or ligation of internal or external iliac artery, uterine cavity stuffing with gauze or water sac compression to stop bleeding, partial implant resection and repair, placenta retention Surgery methods such as stagnation in place, embolism, mifepristone or MTX, preoperative placement of the internal iliac artery, and intraoperative intervention if necessary, can minimize bleeding and blood transfusion. However, due to the inevitable bleeding, it is necessary to prepare a large number of blood sources. In order to save the life of the mother, hysterectomy or even excision of the placental invasion and bladder is required. ^[3]

references:

1. Cao Zeyi and others. Chinese Obstetrics and Gynecology: People's Medical Publishing House, 1999: 389-394.

2. Zhao Yangyu. Penetrating placenta of scar after cesarean section: Chinese Journal of Obstetrics and Gynecology, 2009: 10 (4): 245-247.

3. Zhao Yangyu and others. Surgical options for suspicious penetrating placenta implantation before surgery: Chinese Journal of Obstetrics and Gynecology, 2008: 9 (6): 443-446.