Anterior vessel

Introduction of prevascular Vasapraevia is a very rare obstetric disease. It is characterized by painless vaginal bleeding in the middle and late stages of pregnancy. It is easily misdiagnosed as delayed delivery of placenta previa or early exfoliation of the placenta. basic knowledge Sickness ratio: 0.0001% Susceptible population: pregnant women Mode of infection: non-infectious Complications: fetal distress

Anterior vascular cause

(1) Causes of the disease

The etiology of the anterior vessel is unknown. The following are unsubstantiated hypotheses. In 1900, Franque believed that under normal conditions, the pedicle (the primordial base of the umbilical cord) always has the chorion that is in contact with the most abundant decidua. Stretching to the fetus; if in the early pregnancy, the most abundant part of the blood supply is the sacral membrane, the pedicle originates from this, but as the pregnancy progresses, the most abundant area of blood supply has moved the aponeurosis, where the placenta is formed. However, the body pedicle is still in place, where the villi have shrunk into a smooth chorion, and the blood vessels in this part are distributed in a sail shape, and the umbilical cord is attached to the edge of the placenta. Later, Strausman (1902) proposed a sail-like umbilical cord. At the beginning, the placenta is planted in the sacral membrane. Later, due to the better regional extension of the placenta to the blood, the umbilical cord originally attached to the central part gradually becomes eccentric to the edge, and the leaves of the placenta surrounding the attachment become degraded. The chorion has finally developed into a sail-like attachment of the umbilical cord, and Benirschke and Driscoll (1967) hold the same view.

The risk factors associated with pre-vascularization are more related to placental abnormalities. Progenitor vessels are prone to occur in placenta previa, bilobal placenta, para-placenta, and multiple pregnancies, especially in the twins. 10%, it is easy to accompany the pre-vascular, there are reports of increased fetal malformations in the pre-vascular, such as urinary tract malformation, spina bifida, ventricular septal defect, single umbilical artery.

(two) pathogenesis

The pathogenesis is still unclear. During embryonic development, the pedicle is the primordial base of the umbilical cord. Under normal circumstances, the pedicle extends from the chorion that is in contact with the most abundant decidua of the blood supply to the fetus. Franqua (1900) proposes early pregnancy. It is possible that the blood supply is the most abundant aponeurosis is the sacral membrane and the pedicle is the origin of this. As the pregnancy progresses, the blood supply rich area moves to the basal aponeurosis (the future placenta), while the pedicle remains in place. The chorion atrophy becomes a smooth chorion, and the umbilical cord is attached to the umbilical vessel and the umbilical vessel extends to the edge of the placenta. In short, the umbilical cord occurs opposite the implantation of the blastocyst, Benirschke and Driscoll (1967) believe that, at the beginning, The umbilical cord adheres normally, and then the leafy villi are used to find the decidual part with better blood supply, so as to absorb more nutrients and grow in one direction, the umbilical cord is left behind, and the villi of the attachment is atrophied due to malnutrition, and becomes a smooth chorion. This statement is more reasonable, can explain the umbilical cord-like attachment between the two-leaf placenta; it can also explain that in the twin pregnancy, two blastocysts close to the bed often umbilical-sail-like attachment due to the competition for the site, and the umbilical sail Appearance occurs in the uterus Prior to this segment of the fetal, dispersed over the vessel neck inside the mouth of the cervix, pre-formed blood vessels.

Prevascular prevention

Although the pre-vascular is rare, clinical and B-ultrasound doctors should fully understand the disease, strengthen prenatal examination, prenatal diagnosis, and pay close attention to changes in vaginal bleeding and fetal heart rate for pregnant women with high risk factors. Possible improvement in perinatal outcomes.

1. Regular prenatal checkups, early detection of the condition, such as reducing activity during the middle and late pregnancy, preventing constipation, not doing vaginal examination, anal examination, after the fetus is mature, selective cesarean section.

2. If the diagnosis is confirmed in the labor process, the fetus is still alive, and the fetus rate is still regular. It should be rescued by rapid cesarean section.

3. Sexual life is prohibited in the third trimester to avoid rupture of the premature blood vessels, resulting in unnecessary fetal damage to pregnant women.

Prevascular complications Complications

The main complications are fetal distress and even fetal death.

Pre-vascular symptoms common symptoms fetal bradycardia sinus fetal heart rate fetal membrane rupture fetal heart rate irregular fetal heart rate change hypotension

The performance of the anterior blood vessels is not static. Some vascular ruptures of the pre-vascular vessels occur before the rupture of the membranes. They can occur during antenatal or labor, sometimes clots occur at the rupture of the blood vessels, and may be rupture of small veins due to hemorrhage. After the fetus has hypotension, the blood flow slows down and clots appear, so the bleeding stops, but the bleeding can be repeated again. If the amount of bleeding is less, the fetal heart rate can be unchanged, but the amount of bleeding is slightly more, and the fetal heart rate is often There are changes, at this time should be suspected and pre-vascular, if the timing is confirmed to be the disease, immediate treatment often save the possibility of the fetus, sudden bleeding in the artificial rupture of the membrane should be suspected of the possibility of pre-vascular, sometimes artificial rupture There was no bleeding at that time, but bleeding occurred later. At the beginning of the system, the rupture of the membrane did not involve the anterior blood vessels, but when the rupture of the membrane was enlarged, the anterior blood vessels were torn and hemorrhage. In rare cases, the bleeding time was long. For several hours, but the fetus still survivors, the fetal heart rate can still show the sinus fetal heart rate.

The first declination of the blood vessels that are attached to the sails is also a cause of intrauterine distress and death. This is often neglected. The compression of the sail vessels can cause deceleration of the fetal heart rate and bradycardia. Curl et al. tried to compress the anterior blood vessels by hand and found fetal bradycardia within 30 s. According to scholars' estimates, 50% to 60% of fetal deaths were forced by vascular pressure in the anterior blood vessels.

The change in fetal heart rate is not a specific change in the anterior blood vessel, but its appearance should allow the obstetrician to consider the possibility of the anterior blood vessel, and should make a diagnosis as soon as possible and treat it immediately.

Vaginal examination sometimes occasionally finds the anterior blood vessels. For example, Benekiser, the world's first report of the anterior blood vessels, is a blood vessel that is found to have no pulsation during vaginal examination. If there is a pulsating blood vessel, the diagnosis can be confirmed, such as Carp et al. In this case, the pre-vascular was diagnosed in one of the three pregnancies, and the fetus survived after cesarean section.

Front vessel examination

Laboratory testing

1. Observing the source of red blood cells under the microscope Generally, the observation of nucleated red blood cells to distinguish the source of bleeding. If there are more nucleated red blood cells, it suggests that the blood is likely to come from the fetus, but this is not a very characteristic method.

2. ApT test take vaginal blood 2 ~ 3ml, add the same amount of water, centrifuge at 2000r / min (rev / min), collect the supernatant and add 1% NaOH, observe 2min, such as maternal blood, the color is brown If it is fetal blood, it is still pink.

3. Ogita test take 1 drop of vaginal blood and add 5 drops of alkaline solution (0.1g molecular weight KOH) for 2min, add 10 drops of pre-prepared solution (400ml of 50% saturated ammonium sulfate and 1ml of 10g molecular weight hydrochloric acid), The mixture was pipetted onto the filter paper to form a circle with a diameter of 20 mm. Within 30 s, if the hemoglobin and cell debris were denatured, the center was still centered, and the anti-alkaline fetal hemoglobin formed a colored circle around it.

4. Loendersloot test takes 0.1g molecular weight KOH 10ml, plus a few drops of vaginal blood. If it is fetal blood, the test tube is still pink. If it is maternal blood, the color will change to brownish yellow within 20s.

5. Protein electrophoresis test This method takes about 1 hour, first dilute vaginal blood with Beckman hemolysis test agent, then dilute it with maleic acid buffer solution 5 times, then carry out electrophoresis of hemolyzed substance. High, but it must be a certain equipment, and it takes a long time.

6. Kleihauser test blood into a blood smear, air dried for 20min, and fixed in 80% ethanol for 5min, rinsed gently with running water, dried, and then placed in the lotion (FeCl3 14.8mmol / L and Hemastoxylin 16.5mmol / L) 20s, rinsed gently with running water, then stained with ergthrosin 0.1g / 100ml for 2min, then washed with water, dried, microscopic examination, such as cells containing fetal hemoglobin (Hb-F) will be obvious Reddish brown, such as adult hemoglobin (Hb-A), looks like "phantom."

For the above methods, the merits and demerits should be evaluated according to their sensitivity, specificity, complexity of the experiment and reporting speed. Odansi et al. (1996) listed the above methods as follows:

In summary, the Ogita method is simple and easy, and the fetal blood concentration can be positive by 20%. The test time is only 5 minutes. Therefore, the cause of vaginal bleeding is unknown. Seeing too much red can be used to know whether there is a pre-vascular. It is necessary to pay attention to the reagent label and replace it once a month. It is best to have a positive control group to ensure the accuracy.

Film degree exam

1. Ultrasound examination In 1987, Gianopoulos et al first diagnosed the anterior blood vessel with ultrasound. This case is a low placenta. There is a placenta above the cervix. Here, the vascular pulsation is seen. Therefore, it is believed that there may be umbilical cord. Pu'er ultrasound was determined to be a fetal blood vessel, but the position of the blood vessel was fixed several times. Therefore, it was suspected to be a pre-vascular, and a selective cesarean section was performed at 40 weeks of gestation, and a live baby was obtained, and this was confirmed as a pre-position. In 1988, Hurluy was diagnosed as a pre-vascular at 18 weeks of gestation and 27 weeks of gestation by prenatal ultrasound. The 2 cases were bilobal placenta, the second case had repeated prenatal hemorrhage, and 2 cases were At 37 to 38 weeks of gestation, cesarean section was performed, each had a live baby, and the placenta was confirmed to have a pre-vascular.

Nelson was the first to use transvaginal ultrasound with ultrasound Doppler to detect the anterior blood vessel in 1990. Nelson et al believe that vaginal ultrasound is more clear than abdominal ultrasound, and it is difficult to display images of abdominal ultrasound, and it can be determined. The relationship between the mouth and the future is increasing, and it has proven to be an important means of diagnosing the pre-vascular.

In order to avoid the damage caused by the frontal blood vessels to the fetus, Lee et al. reported in 2000 that in a hospital, 93,874 pregnant women were performed from January 1991 to December 1998 in the second trimester and third trimester. There were abnormal blood vessels and vaginal ultrasound and Doppler ultrasound to confirm the diagnosis. As a result, 18 pregnant women had prevascular vessels, and the first one was found to be 15.6 weeks. Eight patients showed that the edge of the placenta was close to the inner mouth and the last placenta "retracted". After the emergence of the pre-vascular, 6 cases with mild bleeding at an average of 31.3 weeks, 3 cases in the third trimester of pregnancy B turned into normal and vaginal delivery, the remaining 15 cases of cesarean section termination of pregnancy, 2 cases of twins each There was 1 death, 1 case of gestational age was only 26 weeks, and 1 case of premature infant died of 3 cases of postpartum due to various diseases such as hyaline membrane disease. Ten of the placenta examination showed umbilical cord-like attachment and 3 cases of bilobal placenta. There were 2 cases of para-placenta and 2 cases of umbilical placenta edge. This report is the result of systematic examination of a single hospital for nearly 10 years, so it is very representative.

According to the actual experience of Oyelese et al (1999), placental positioning can be performed at the first B overtime at 20 weeks of gestation, providing possibility for the presence or absence of pre-vessels, and for all high-risk pregnant women, especially multiple pregnancies, placenta low, double The placenta and the placenta have transvaginal ultrasound and Doppler examination, which also includes IVF-ET pregnancy.

The anterior blood vessels are summarized according to Dougall and Baind (1989), and the transvaginal and perineal ultrasound and color Doppler examination methods developed in recent days can be summarized into six types, namely: 1 by ultrasound. Vascular (unruptured); 2 vaginal examination of iliac crest and anterior blood vessels (unruptured); 3 unruptured membranes and ruptured anterior vessels; 4 ruptured anterior vessels when natural membranes rupture; 5 ruptured anterior vessels when ruptured artificially ; 6 front blood vessels are under pressure.

Before the diagnosis with ultrasound, it is often known that there is a placental lesion due to vaginal bleeding, and it is very easy to be misunderstood as a placenta previa, because the blood volume of the fetal full-term pregnancy is about 250ml, such as blood loss more than 20% to 25%, that is, Corresponding to about 60ml, hemorrhagic shock can occur, and more blood loss without timely treatment will inevitably lead to fetal death.

2. Magnetic resonance imaging (MRI) is also a method for examining prevascular vessels. The accuracy is high. Nimmo et al. (1988) have reported it, but its cost is high, so it is difficult to promote the disease with MRI.

3. Amnioscopy Amnioscopy directly through the amniocentesis is very reliable way to see the sail through the cervix, Browne et al (1968) used this method to do 3589 amniocentesis in 1434 pregnant women found 2 cases Pre-vascular, but this method also has its limitations, Young et al (1991) used this method to combine with B-ultrasound, found two patients with pre-vessels missed by B-ultrasound screening, the author also believes that the front Vascular prone to occur in bilobed placenta or with placenta, low placenta, multiple placenta, IVF pregnancy, bleeding during labor or irregular fetal heart rate, etc. When performing amniocentesis before artificial rupture will help Found a frontal blood vessel.

Pre-vascular diagnosis

Application of color Doppler ultrasound (transvaginal) prenatal diagnosis of anterior blood vessels can reduce fetal mortality. Lee et al (2000) observed the endocervical sinus of 93,748 middle and late pregnant women within 8 years. A parallel or circumferential echo line near the inner cervix is confirmed by a transvaginal color Doppler ultrasonography as a pre-vascular. If prenatal misdiagnosis, the main points of identifying the pre-vascular after labor are:

1. During vaginal examination, through the dilated cervix, there is a pulsating artery on the membrane of the pre-exposed part of the fetus.

2. When the fetal heart is irregular in the labor process, the amniocentesis before the rupture of the membrane has diagnostic value.

3. When the membrane is ruptured, the vaginal bleeding, with fetal heart rate changes, irregular, or even disappear.

4. Take vaginal blood smear examination, find nucleated red blood cells or young red blood cells, immature or imminent red blood cells can only come from fetal blood, take vaginal blood for protein electrophoresis, and find that fetal hemoglobin band can also prove to be anterior vessel rupture.

It must be differentiated from low placenta, I degree placental abruption and placental sinus rupture. B-ultrasound can be distinguished.

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