placenta previa
Introduction
Introduction to placenta previa The normal placenta is attached to the posterior wall, anterior wall or side wall of the uterus. If the placenta is attached to the lower part of the uterus, and even the lower edge of the placenta reaches or covers the inner opening of the cervix, its position is lower than the first exposed part of the fetus, called the placentaprevia. Placenta previa is one of the main causes of late pregnancy bleeding, and is a serious complication during pregnancy. Improper handling can endanger the safety of mother and child. The incidence rate is 0.24% to 1.57% in domestic reports and 1.0% in foreign countries. 85% to 90% of patients with placenta previa are maternal, especially multi-partum, with a prevalence of up to 5%. basic knowledge The proportion of sickness: 0.01% Susceptible people: maternal Mode of infection: non-infectious Complications: postpartum hemorrhage puerperal infection anemia
Cause
Anterior placenta
Causes
The cause is not completely clear, but after extensive research by scholars at home and abroad, it has been initially determined that it may be related to the following factors.
Endometrial lesions in the uterus (25%):
Such as puerperal infection, prolific sputum, multiple curettage and cesarean section, etc., causing endometritis or endometrial damage, resulting in uterine decidual vascular insufficiency, when fertilized eggs are implanted, blood supply is insufficient, in order to ingest Enough nutrition to expand the placenta area and stretch to the lower part of the uterus.
Fertility egg trophoblast developmental delay (20%):
When the fertilized egg reaches the uterine cavity, it has not yet developed to the stage of implantation, and continues to be transplanted into the lower uterus, where it grows and forms a placenta previa.
Excessive placenta area (10%):
For example, the placenta area of the twins is larger than that of the single fetus and reaches the lower part of the uterus. The incidence of placenta previa in twins is twice as high as in singles.
Abnormal placenta (15%):
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.
Prevention
Placenta previa prevention
1, to avoid heavy objects: in the middle and late pregnancy, life details should be more careful, it is not appropriate to carry heavy objects or abdominal output, so as to avoid danger.
2, depending on the situation, suspend sexual behavior: if there is bleeding symptoms or enter the late pregnancy, it is not appropriate to have sexual behavior, in addition, patients with mild placenta previa, also to avoid too intense sexual behavior or oppression of the abdomen.
3, bleeding should be treated immediately: when there is bleeding symptoms, regardless of the amount of blood should be immediately treated, if you encounter a new doctor, you should also be informed of the problem of placenta previa.
4, do not be too tired: pregnant women with high-risk pregnancy should rest more, avoid too tired and affect the smoothness of pregnancy.
Complication
Placenta previa complications Complications, postpartum hemorrhage, puerperal infection, anemia
1. Postpartum hemorrhage: After delivery, due to the poor contractility of the lower uterine muscle tissue, the sinusoids attached to the placenta after exfoliation are not easy to tighten and close, so they often produce bleeding after production.
2, implantable placenta: factor uterine dysplasia and other reasons, placental villi can be implanted into the myometrium, causing incomplete bleeding of the placenta and major bleeding.
3, puerperal infection: the placenta stripping surface of the placenta previa is close to the external cervix, bacteria easily invade the placenta from the vagina, most of the maternal anemia, physical weakness, prone to infection.
Symptom
Pre-placental symptoms common symptoms Placental pre-existing blood loss too much fetal position abnormal anterior uterus late pregnancy or labor... Blood pressure drop repeated bleeding anemia appearance sheep bloody pale
1, symptoms
In the third trimester or at the time of labor, the painless recurrent vaginal bleeding is the main symptom of the placenta previa. Occasionally, it occurs in the 20th week of pregnancy. The bleeding is due to the late extension of the lower uterus and the disappearance of the cervix. When the cervix is dilated, the placenta attached to the lower part of the uterus or the internal cervix cannot be stretched accordingly, causing the placenta of the anterior portion to be detached from the attachment, causing rupture of the sinusoids and bleeding, and the initial blood flow is generally small, and the detachment is After blood coagulation, the bleeding can be temporarily stopped. Occasionally, there are cases of the first time with a large amount of bleeding. As the lower part of the uterus continues to stretch, the bleeding often occurs repeatedly, and the amount of bleeding is also increasing. The time of vaginal bleeding occurs sooner or later. The number of occurrences, the amount of bleeding has a great relationship with the type of placenta previa. Complete placenta previa often has early bleeding time, about 28 weeks of gestation, frequent repeated bleeding, more quantity, sometimes once A large amount of bleeding can cause the patient to fall into a state of shock. The marginal placenta previa is the first time in the enemy country, mostly in the 37- to 40-week pregnancy or in labor. The amount of initial bleeding and the amount of bleeding in the partial placenta previa are between the above two. Partial or marginal placenta previa patients, the rupture of the membrane is conducive to the compression of the placenta before the membrane is broken. If the first exposure of the fetus can drop rapidly, the placenta can be directly compressed, and bleeding can be stopped.
Due to repeated or a large number of vaginal bleeding, patients may have anemia, the degree of anemia is directly proportional to the amount of bleeding, severe bleeding can occur in shock, fetal hypoxia, distress, and even death.
2, signs
The general condition of the patient depends on the amount of bleeding. When there is a large amount of bleeding, there may be a pale complexion, a weak pulse, a drop in blood pressure, etc. Abdominal examination: the size of the uterus is consistent with the number of menopause weeks, and the lower part of the uterus has a placenta occupying, affecting the first exposure of the fetus. Potted, so the first exposed part of the high floating, about 15% of the abnormal fetal position, especially for the breech position, check at the time of labor: contractions for paroxysmal, intermittent uterus can be completely relaxed, sometimes can hear placental murmur above the pubic symphysis .
Examine
Pre-placenta examination
1, ultrasound examination
2, magnetic resonance imaging
This is also one of the methods for detecting placental abnormalities such as placenta previa without damage. However, the method of checking the method is complicated and expensive, so it cannot replace the B-ultrasound.
3. Contrast agent cystography and radionuclide scanning
Contrast agent cystography is a mechanism in which the placenta is embedded between the fetal head and the bladder to make a large interval. After filling the bladder, positive and lateral angiography is performed on the X-ray to the upright position of the pregnant woman. The distance between the two is more than 2 cm to diagnose the placenta previa. However, the accuracy of this method is not high, the breech position is not applicable, and the radiation is harmful to both the mother and the child, so it is not used now. The radionuclide 113mIn (113m indium) was used to check the placenta previa, but the accuracy and the difference in the type of placenta previa are not as good as the B-ultrasound method, and special equipment is required, so it has also been replaced by B-ultrasound.
4, postpartum examination of placenta and fetal membrane
The shape of the postpartum placenta is generally larger, thinner, sometimes oblong or irregular, and a few have a placenta. The placenta pre-position is often accompanied by dark brown old blood clots, and the vertical distance between the edge of the membrane and the edge of the placenta within 7cm can be diagnosed as low placenta.
Diagnosis
Diagnosis of placenta previa
diagnosis
1. History: There is no painful repeated vaginal bleeding in the third trimester or at the time of labor. It 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, physical signs: according to the amount of blood loss, multiple bleeding, anemia, acute massive bleeding, shock can occur, in addition to the first exposure of the fetus and sometimes high floating, abdominal examination is the same as normal pregnancy, excessive blood loss can occur in the fetus intrauterine Hypoxia, severe cases of fetal death, sometimes can be heard above the pubic symphysis, but can not be heard when the placenta is attached to the posterior wall of the lower uterus.
3, vaginal examination: generally only for vaginal peeping and sputum percussion, should not be referred to the neck tube, so as not to cause the placenta attached to the placenta caused by massive bleeding, if the complete placenta previa, even life-threatening, vaginal examination Applicable to the diagnosis before termination of pregnancy and determine the mode of delivery, must be carried out under the conditions of infusion, blood transfusion and surgery, if the diagnosis is clear or excessive bleeding should not be vaginal examination, B-mode ultrasound is widely used in recent years, Vaginal examinations have rarely been done.
Inspection method: After strict disinfection of the vulva, check with vaginal speculum to observe the presence or absence of vaginal wall varices, cervical polyps, cervical cancer or other lesions causing bleeding. After peeping, use one hand to show, the middle two fingers in the vaginal fistula around the cervix Gently palpate, if the sputum is clearly removed, the placenta can be excluded. If there is a thick soft tissue (placenta) between the finger and the first dew, it should be considered as the placenta previa, if the cervix has Partial dilatation, no active bleeding, can gently index the finger into the cervix, check for the presence of sponge-like tissue (placenta), if the blood clot is brittle, pay attention to the relationship between the edge of the placenta and the cervix to determine the placenta previa Type, if you touch the membrane and decide to break the membrane, you can puncture the membrane.
4, ultrasound examination: B-mode ultrasound tomography can clearly see the location of the uterine wall, the first exposed part of the fetus, the placenta and the cervix, and further clarify the type of placenta previa according to the relationship between the edge of the placenta and the internal cervix, accurate positioning of the placenta The rate is as high as 95% or more, and can be repeatedly checked. It has been widely used at home and abroad in recent years, basically replacing other methods, such as radioisotope scanning and localization, indirect placental angiography.
B-mode ultrasound diagnosis of placenta previa should pay attention to the number of weeks of pregnancy, the placenta in the second trimester occupies half of the uterine cavity area, therefore, the placenta near the cervix or the inner mouth more opportunities, until the third trimester of the placenta accounted for less uterine cavity area Up to 1/3 or 1/4; while the formation and extension of the lower uterus increases the distance between the cervix and the edge of the placenta, so the placenta that seems to be in the lower part of the uterus can change to the normal placenta with the uterus moving up, so If mid-pregnancy B-mode ultrasound findings of low placenta position, do not premature diagnosis of placenta previa, regular follow-up without vaginal bleeding symptoms, 34 weeks before pregnancy is generally not diagnosed with placenta previa.
5, postpartum examination of placenta and fetal membranes for prenatal bleeding patients, should be carefully examined after delivery of the placenta, in order to verify the diagnosis, the placenta of the placenta has black and purple old blood clots attached, if the membrane breaks from the edge of the placenta distance <7cm It is a partial placenta previa.
classification
Where the placenta covers the internal cervix or close to the cervix, it is called the placenta previa, and there are two types of placenta previa:
(1) Level 4 classification:
1 Complete placenta previa: The internal cervix is completely covered by the placenta.
Partial placenta previa: The inner part of the cervix is covered by the placenta.
3 marginal placenta previa (marginal placenta previa): the edge of the placenta is just next to the cervix.
4 low-lying placenta: the placenta is implanted in the lower part of the uterus, although the edge of the uterus is not up to the end of the cervix, but close to it.
(2) Level 3 classification:
1 Complete placenta previa: The internal cervix is completely covered by the placenta.
Partial placenta previa: The inner part of the cervix is covered by the placenta.
3 marginal placenta previa (marginal placenta previa): placenta is implanted in the lower part of the uterus, the edge does not exceed the inner cervix, the above two classification methods, because the placenta is low, the clinical impact is small, and the marginal placenta previa It is confusing, so the current level 3 classification is commonly used.
Due to the expansion of the cervix after the late pregnancy, the relationship between the cervix and the placenta can be changed. For example, the marginal placenta previa before labor, the cervix is enlarged after the delivery and becomes a partial placenta previa, so the classification should be based on the treatment. It depends on the last inspection.
Differential diagnosis
1, placental abruption: severe placental abruption showed sudden persistent abdominal pain, backache, low back pain, no vaginal bleeding or a small amount of vaginal bleeding, the degree of anemia is not consistent with the amount of external bleeding, the uterus is as hard as a plate, but light The placental abruption is sometimes similar to the clinical manifestation of the placenta previa. B-ultrasound can detect post-placental hematoma and has a diagnostic value for the diagnosis of placental abruption.
2, cervical polyps: When examining the cervix, there are tongue-like protrusions outside the cervix, which is easy to hemorrhage. Pathological biopsy can confirm cervical polyps.
3, cervical cancer: the incidence of pregnancy associated with this disease is low, when the cervix is examined, the cauliflower-like sputum on the cervix is found, the bleeding is easy to touch, and the pathological biopsy can confirm the diagnosis.
