The normal laying of placental tissue is an important condition for the physiological course of pregnancy. This article will explain what placenta previa is and how it affects pregnancy and childbirth.
Definition
Ancient doctors called the placenta a “child's place”. Even from Latin the word "placenta" is translated as "child's place", "afterbirth", "flat cake". All these comparisons clearly describe the placental tissue.
The placenta is formed only during pregnancy. Through it, the baby receives all the nutrients necessary for its growth and intrauterine development, as well as oxygen. Numerous blood vessels pass through the “baby seat”, which ensure uninterrupted blood flow between mother and child. Such a unique circulatory system, which occurs only during the period of gestation, is called the uteroplacental blood flow system.
The embryonic membranes of the chorion are involved in the formation of the placenta. They form dense, fleecy outgrowths that tightly penetrate the wall of the uterus. This attachment provides fixation of the placental tissue. During childbirth, it is separated after the baby is born and is called the "afterbirth".
Normally, the placental tissue forms slightly higher than the internal os of the uterus is located. In the 2nd trimester of pregnancy, the placenta should normally be 5 cm higher than the throat. If for some reason the placental tissue is located lower, then this is already a sign of a placental defect - low attachment of the placenta.
In the 3rd trimester of pregnancy, the placental tissue is normally located at a distance of approximately 7 cm from the internal os. Determining the location of the placenta is quite simple. For this, ultrasound examinations are used. With these simple diagnostic procedures, doctors can fairly accurately determine how high up the placental tissue is.
If the placenta is located in the lower parts of the uterus and even touches the internal os, then this clinical condition is called presentation. In such a situation, the placental tissue can partially "enter" the pharynx or even completely block it. According to statistics, this condition occurs in approximately 1-3% of all pregnancies.
Normal location
In most cases, the placenta forms at the back of the uterus. It can also go to the side walls - both to the right and to the left. There is a fairly good blood supply in the area of the uterine fundus and back wall. The presence of blood supply vessels is necessary for the full intrauterine development of the fetus. The correct location of the placenta ensures the physiological growth of the developing baby in the mother's womb.
Placental tissue is rarely attached to the anterior wall of the uterus. The thing is that this zone is quite sensitive to various influences. Mechanical damage and trauma can damage the rather soft tissue of the placenta, which is an extremely dangerous condition.
Rupture of the placenta is dangerous by the complete cessation of the blood supply to the fetus, and hence the development of acute oxygen deficiency.
If the pathology of the normal position of the placenta was detected at 18-20 weeks, then this is not a reason to panic. The possibility of displacement of placental tissue before the onset of labor is still quite high. This is influenced by a huge variety of factors. Revealing placenta previa at a fairly early stage allows doctors to fully monitor the course of pregnancy, which means it improves the potential prognosis.
Causes of occurrence
A number of different factors lead to a change in the place of attachment of placental tissue. In fact, the location of the placenta is determined after fertilization. A fertilized egg should normally attach to the bottom of the uterus.
In this case, in the future, the placental tissue will attach correctly. If, for some reason, the embryo implantation does not take place in the area of the uterine fundus, then in this case the placenta will be nearby.
The most common and common cause leading to the development of placenta previa is the consequences of various gynecological diseases, accompanied by inflammation of the inner wall of the uterus (endometrium). Chronic inflammation damages the delicate lining of the uterus, which can affect the attachment of placental tissue. In this case, the ovum simply cannot fully attach (implant) into the wall of the uterus in the area of its bottom and begins to sink lower. As a rule, it moves to the lower parts of the uterus, where it is attached.
Also, the development of placenta previa can be facilitated by various surgical gynecological interventions carried out even before pregnancy. This can be curettage, cesarean section, myomectomy and many others. The risk of the formation of placenta previa in this case is much higher in the first year after the surgical treatment.
The more time has passed since the gynecological operations performed, the less likely a woman will have placenta previa during a subsequent pregnancy.
Doctors note that in multiparous women, the risk of developing previa is slightly higher than in primiparous women. Scientists are currently conducting experiments aimed at studying the genetic factor of the possibility of developing placenta previa during pregnancy. So far, there are no reliable data on the influence of genetics on the development of this pathology in close relatives.
Studying numerous cases of pregnancies occurring with the development of placenta previa, doctors have identified high-risk groups. They include women with a number of specific health characteristics. In these women, the risk of developing placental previa or its low location is quite high.
The high-risk group includes patients who have:
- the presence of a burdened obstetric and gynecological history (previous abortions, surgical curettage, previous difficult labor and much more)
- chronic gynecological diseases (endometriosis, salpingitis, vaginitis, myoma, endometritis, cervical disease and others);
- hormonal pathologies associated with ovarian pathology and accompanied by a violation of the regularity of the menstrual cycle;
- congenital anomalies in the structure of the female genital organs (underdevelopment or prolapse of the uterus, ovarian hypoplasia, and others).
If a woman falls into a high-risk group, then doctors monitor the course of her pregnancy quite closely. In such a situation, the number of vaginal examinations performed is minimized. Also, preference in diagnosis is given to transabdominal ultrasound, rather than transvaginal. Already in the early stages of pregnancy, the expectant mother draws up individual recommendations aimed at minimizing the likelihood of her developing unfavorable symptoms of placenta previa pathology.
Clinical options
Experts identify several possible clinical situations, how the placental tissue can be located relative to the internal os of the uterus. These include:
- full presentation;
- partial (incomplete) presentation.
With full presentation, the placental tissue almost completely overlaps the area of the internal os. This situation, according to statistics, develops in 20-30% of all cases with placenta previa.
Obstetricians-gynecologists speak of partial presentation if the placenta passes to the internal pharynx only partially. This pathology is already encountered somewhat more often - in approximately 70-80% of all pregnancies with placenta previa.
Classification
It is possible to assess the degree of overlap of the placental tissue of the internal os using ultrasound. Doctors use a special classification that allows for different clinical options. Taking into account the assessed signs, this pathology can be:
- 1 degree. In this case, the placental tissue is quite close to the opening of the cervix. Its edges are 3 cm higher than the inner pharynx.
- 2 degrees. In this case, the lower edge of the placenta is practically located at the entrance to the cervical canal without overlapping it.
- 3 degrees. The lower edges of the placenta begin to overlap the internal uterine pharynx almost completely. In this situation, the placental tissue is usually located on the anterior or posterior uterine wall.
- 4 degrees. In this case, the placental tissue completely blocks the entrance to the cervical canal. The entire central part of the placenta "enters" the area of the internal uterine pharynx. At the same time, both on the anterior and posterior walls of the uterus there are separate areas of placental tissue.
In addition to ultrasound examinations, obstetricians-gynecologists also use old proven methods of diagnosing various options for the location of the placenta. These include vaginal examination. An experienced and qualified doctor can quickly and accurately determine where the "child's place" is. At the same time, it can have the following localizations:
- Center. This type of presentation is called the central presentation of the placenta - placenta praevia centralis.
- On the sides. This variant of presentation is called lateral or placenta praevia lateralis.
- Around the edges... This variant is also called marginal or placenta praevia marginalis.
There are a number of correspondences between ultrasound and clinical classification. So, for example, the central presentation corresponds to 3 or 4 degrees by ultrasound. Its experts also call it complete. Grade 2 and 3 by ultrasound corresponds, as a rule, to lateral presentation.
The marginal presentation of the placental tissue is usually equivalent to 1-2 degrees by ultrasound. Also, this clinical variant can be called partial.
Some doctors use an additional clinical classification. They divide the presentation at the site of attachment of the placental tissue to the uterine walls. So, it can be:
- In front of him. In this situation, the placental tissue is attached to the anterior uterine wall.
- Back. The placenta, for its most part, is attached to the back wall of the uterus.
It is possible to accurately determine to which wall the placental tissue is attached, as a rule, up to 25-27 weeks of pregnancy. However, it is important to remember that the position of the placenta can change, especially if it attaches to the anterior wall of the uterus.
Symptoms
It should be noted that placenta previa is not always accompanied by the development of unfavorable clinical signs. With partial presentation, the severity of symptoms may be very slight.
If the placental tissue significantly overlaps the internal pharynx of the uterus, then the pregnant woman begins to develop adverse manifestations of this pathology. One of the possible symptoms inherent in presentation is the occurrence of bleeding. As a rule, it develops in the 2nd trimester of pregnancy. However, in some women, bleeding from the genital tract develops much earlier - at the very early stages of bearing a baby.
In the final 3rd trimester of pregnancy, the severity of bleeding may increase. This is largely due to the intense contractions of the uterus, as well as the advancement of the fetus down the genital tract. The closer the upcoming birth, the higher the chance of developing severe bleeding.
Doctors believe that the main reason for the appearance of blood from the genital tract in this case is the inability of the placenta to stretch following the stretching of the uterine walls. The approaching onset of labor contributes to the fact that the placenta begins to exfoliate, which is manifested by the appearance of bleeding.
In this case, it is important to understand that the fetus does not lose its own blood. In this situation, only ruptures of the placental tissue itself occur. The danger of this condition is that the baby, "living" in the mother's tummy, may begin acute oxygen starvation - hypoxia.
The appearance of bleeding in placental tissue previa, as a rule, is facilitated by any influence. So, it can develop after:
- lifting heavy objects;
- physical activity and running;
- severe cough;
- careless vaginal examination or transvaginal ultrasound;
- sex;
- performed thermal procedures (baths, saunas, baths).
With full presentation, blood from the genital tract may appear suddenly. It usually has an intense bright red color. In this case, the pain symptom may or may not be. It depends on the individual condition of the pregnant woman. After a while, the bleeding usually stops.
With incomplete presentation, bleeding from the genital tract of a pregnant woman most often develops in the 3rd trimester of pregnancy and even with the immediate onset of labor. The severity of bleeding can be very different - from scanty to intense. It all depends on how much the placenta overlaps the internal uterine pharynx.
Placenta migration
During pregnancy, the position of the placenta may change. This process is called migration. It is largely due to the physiological changes in the lower parts of the uterus, which develop at different weeks of pregnancy.
The best prognosis is usually anterior wall migration of the placenta. In this situation, the placental tissue moves slightly upward, changing its original location. If the placenta is attached to the posterior wall, then its migration is usually difficult or extremely slow. In practice, there are cases when the placental tissue attached to the posterior wall of the uterus did not move during pregnancy.
Placental migration is usually a slow process. Optimally, it occurs within 6-10 weeks. In this case, the pregnant woman does not experience any adverse symptoms. The process of migration of the placenta usually ends by 33-34 weeks of gestation.
If the placental tissue changes its position too quickly (in 1-2 weeks), then this can be dangerous for the development of certain symptoms in the expectant mother. So, a pregnant woman may feel abdominal pain or notice the appearance of bleeding from the genital tract.
In this case, you should not hesitate in seeking medical help.
What complications can there be?
The development of frequent bleeding is an unfavorable sign. Frequent blood loss threatens the development of an anemic state in a pregnant woman, accompanied by a decrease in iron and hemoglobin in her blood. Mother's anemia is a dangerous condition for the developing fetus. A decrease in hemoglobin in the placental blood flow can contribute to a decrease in the intensity of intrauterine development of a baby, which will negatively affect his health in the future.
Another possible complication of presentation may be the development of spontaneous unplanned delivery. In this case, the fetus may be born much earlier than the due date. In such a situation, the baby may be premature and incapable of independent life.If placenta previa is too pronounced and proceeds rather unfavorably, then in this case there is also a risk of spontaneous miscarriage.
Also, doctors note that patients who have placenta previa during pregnancy often have difficulty maintaining normal blood pressure numbers. A woman may develop hypotension, a condition in which blood pressure drops below the age limit. According to statistics, this pathology develops in 20-30% of pregnancies occurring with placenta previa.
One of the severe complications of gestation is gestosis. This pathology is no exception for women who have placenta previa during pregnancy. Especially often in this case, late gestosis develops. It is accompanied by the development of blood clotting pathology, as well as disorders in the work of internal organs.
Fetal-placental insufficiency is another pathology that can develop with presentation. This condition is extremely dangerous for the fetus. It is characterized by a decrease in the supply of oxygen to the child's body, which negatively affects the development of the child's heart and brain.
Experts have found that when placenta previa, there are often abnormal locations of the fetus in the uterus. For normal physiological development, the baby should be in the head-down position.
However, other clinical variants may develop with placenta previa. So, the fetus can be located in an oblique, pelvic or transverse position. With such options for the location of the child in the uterus, various pathologies may occur during pregnancy. Also, these presentation can become an indication for surgical obstetrics. Quite often, expectant mothers in such situations undergo a cesarean section.
How is the diagnosis carried out?
Placental presentation can be suspected without ultrasound. The presence of this pathology may be indicated by recurrent bleeding from the genital tract in a pregnant woman, usually developing in 2-3 trimesters of pregnancy.
When blood appears from the genital tract, it is very important to conduct a clinical vaginal examination. This excludes any other pathologies that could cause the development of similar symptoms. Also, with this pathology, the general condition of the fetus is necessarily assessed. This is done through an ultrasound examination.
The basic method for diagnosing placental previa today is ultrasound. An experienced doctor can easily determine the degree of overlap of the internal os by the placenta. After the study, the ultrasound specialist gives the expectant mother in her arms the conclusion drawn up by him. It must be included in the medical card of a pregnant woman, as it is necessary to draw up the correct tactics for conducting pregnancy, as well as track it in dynamics.
If, during the ultrasound examination, placental tissue is found in the area of the internal pharynx, then it is undesirable to carry out further frequent vaginal examinations in the future. If necessary, doctors still resort to performing this examination, but they try to perform it as carefully and carefully as possible.
If placenta previa was established early enough, then the expectant mother will be assigned several additional ultrasounds. As a rule, they are carried out sequentially at 16, 25-26 and 34-36 weeks of pregnancy.
Experts recommend an ultrasound scan when the bladder is full. In this case, it becomes much easier for an ultrasound doctor to see pathologies.
With the help of an ultrasound examination, it is also possible to determine the accumulation of blood in case of a hematoma. At the same time, its quantity is necessarily assessed. So, if it is less than ¼ of the total area of the placenta, then such a clinical condition has a rather favorable prognosis for the further course of pregnancy. If the hemorrhage is more than 1/3 of the total area of placental tissue, then in such a situation the prognosis for the life of the fetus is rather unfavorable.
What measures should be taken?
When bleeding from the genital tract appears, it is very important for a pregnant woman to immediately seek advice from her obstetrician-gynecologist. Only a doctor can fully assess the severity of the condition that has arisen and draw up a plan for the further management of pregnancy.
If placenta previa is not accompanied by the development of unfavorable symptoms, then in such a situation the expectant mother may also be under dispensary observation. A pregnant woman will not be hospitalized in a hospital during the normal course of pregnancy. At the same time, the expectant mother is necessarily given recommendations that she should carefully monitor her well-being. Also, recommendations are made that one should not lift weights and intense physical activity is limited. An expectant mother who has placenta previa should also carefully monitor her emotional state.
Severe stress and nervous shock can cause severe spasm of the uteroplacental vessels. The resulting blood flow disorders can be very dangerous for the intrauterine development of the fetus.
Treatment
As a rule, therapy for placenta previa after 24-25 weeks is carried out in a stationary setting. In this situation, doctors try to eliminate the risk of premature birth. In the hospital, it is much easier to monitor the general condition of the expectant mother and baby.
When carrying out therapy, the following principles must be observed:
- compulsory bed rest;
- the appointment of drugs that normalize the tone of the uterus;
- prevention and treatment of anemic condition and possible fetal-placental insufficiency.
If the bleeding is too severe and does not stop, there is severe anemia, then a caesarean section may be performed. A vital operation can be performed when the mother or fetus is in a critical condition.
With full placenta previa, a cesarean section is performed. Vaginal childbirth can be very dangerous. With the onset of labor, the uterus begins to contract strongly, which can lead to rapid placental abruption. In such a situation, the severity of uterine bleeding can be very strong. In order to avoid massive blood loss and for the safe birth of a baby, doctors resort to performing surgical obstetrics.
Caesarean section can be performed routinely and in the following cases:
- if the baby is in the wrong position;
- in the presence of extended scars on the uterus;
- with multiple pregnancies;
- with pronounced polyhydramnios;
- with a narrow pelvis in a pregnant woman;
- if the expectant mother is over 30 years old.
In some cases, with incomplete presentation, doctors may not resort to a surgical method of obstetrics. In this case, they, as a rule, wait for the onset of labor, and with its onset, they open the fetal bladder. An autopsy in such a situation is necessary in order for the head of the fetus to begin the correct movement along the birth canal.
If during natural childbirth heavy bleeding occurs or acute fetal hypoxia develops, then in this case, the tactics usually change and a cesarean section is performed. Monitoring the condition of the woman in labor and the fetus is very important. To do this, doctors monitor several clinical signs at once. They assess uterine contractility, cervical dilatation, pulse and blood pressure in the mother and fetus, as well as many other indicators.
In medical practice, cesarean sections are increasingly being performed. According to statistics, obstetricians-gynecologists prefer this method of obstetric aid in almost 70-80% of all pregnancies occurring with placenta previa.
The postpartum period with placenta previa can be complicated by the development of a number of pathologies. The more difficult the pregnancy was and the more often bleeding developed, the higher the probability of a woman's difficult recovery after pregnancy. She may develop gynecological diseases, as well as dream about the tone of the uterus. Also in the postpartum period, profuse uterine bleeding may appear.
After pregnancy, you should be very careful to monitor the well-being and general condition of the mother, who carried the baby with placenta previa. If a woman feels severe weakness, she is constantly dizzy and bloody discharge continues for several months after giving birth, then she should immediately consult with her gynecologist. In such a situation, it is necessary to exclude all possible postoperative complications, as well as the development of a severe anemic condition.
Prevention
It is impossible to prevent placenta previa 100%. By following certain recommendations, a woman can only reduce the likelihood of developing this pathology during pregnancy. The more responsible the expectant mother will be about her health, the more chances for a healthy baby to be born.
In order to reduce the risk of developing placenta previa, a woman should be sure to regularly visit a gynecologist. It is better to treat all chronic diseases of the female reproductive organs in advance, even before pregnancy. It is very important to carry out therapy for infectious and inflammatory pathologies. They are quite often the root cause of the development of placental previa.
Of course, it is very important to minimize the consequences of surgical interventions performed for various reasons. If a woman decides to have an abortion, then it should be performed only in a medical institution. It is very important that any surgical procedure is performed by an experienced and competent specialist.
Keeping a healthy lifestyle is also quite an important preventive measure. Proper nutrition, absence of severe stress and adequate sleep contribute to the good functioning of the female body.
In the next video, you will learn even more information about the features of the location of the placenta.
