Obstetrics and Gynecology - A. M. Hromova 2000

Obstetric Hemorrhage
Placenta Previa

Placenta praevia is a condition in which the placenta implants in the lower uterine segment, completely or partially covering the internal cervical os. This pathology occurs in 0.3–0.9% of all deliveries.

The primary causes of placenta praevia include: Changes in the uterine mucosa resulting from previous inflammatory processes, significant trauma from artificial abortions and uterine curettage; developmental anomalies, infantilism, uterine fibroids; The Use of intrauterine devices; and a delayed onset of the proteolytic properties of trophoblastic Enzymes.

Placenta praevia is more commonly observed in multiparous than in nulliparous women, with Placental Attachment Anomalies—such as placenta accreta and adherent placenta—occurring several times more frequently.

Placenta praevia is classified into the following types:

1. Complete placenta praevia (placenta praevia centralis), in which the placenta completely covers the internal os of the Uterus.

2. Incomplete (partial) placenta praevia (placenta praevia partialis), where the placenta is located either at the edge of the internal os (marginal placenta praevia) (placenta praevia marginalis) or covers up to 2/3 of it (partial/lateral placenta praevia) (placenta praevia lateralis).

Very rarely, placenta praevia is combined with its partial attachment to the walls of the cervical canal, known as cervical Pregnancy or cervical placenta (placenta cervicalis or placenta isthmicocervicalis).

Given the placenta's capacity for migration—meaning its upward movement along the uterine wall as gestational age advances—placenta praevia is diagnosed 8–10 times more frequently In the second trimester than it is near term.

The most prominent clinical symptom of placenta praevia is Hemorrhage, which occurs in the second half of pregnancy, as well as during the First and Second stages of labor. Such bleeding is characterized by suddenness (appearing without apparent external cause), absence of pain, and a tendency to begin frequently at rest, during the night. Bleeding typically recurs, and its pattern is unpredictable. In the third trimester, hemorrhage can be triggered by physical exertion, sexual intercourse, defecation, or a vaginal examination.

The onset of bleeding during pregnancy is caused by the stretching of the lower uterine segment, which gradually becomes part of the amniotic cavity. Placental detachment is further promoted by uterine contractions, particularly during labor, when each contraction is accompanied by an increase in intra-uterine pressure, causing the placenta and fetal membranes to bulge into the lumen of the internal cervical os. Simultaneously, the walls of the lower uterine segment and the cervix shift due to the retraction of the uterine Muscles, further disrupting the attachment of the placenta to the uterine wall. As a result, the affected area of the placenta prematurely separates from the uterine wall due to the placenta's inability to stretch. The uteroplacental vascular spaces rupture, leading to hemorrhage that may cease in the absence of contractions or intensify if they continue, posing a life-threatening risk to both mother and fetus. Recurrent hemorrhages rapidly lead to anemia in the pregnant woman. Such a patient tolerates Blood loss poorly during delivery, which directly threatens the mother's life.

The course of pregnancy and labor in cases of placenta praevia is frequently pathological: malpresentations of the fetus are observed, along with abnormal HEAD presentations and uterine inertia caused by insufficient pressure exerted on the cervical receptors by the presenting fetal part located at the pelvic inlet. The threat of Miscarriage is also frequently noted.

During the Third Stage of labor, the processes of placental Separation are often impaired because the lower segment of the uterus in the placental site contracts poorly, resulting in bleeding that persists into the postpartum period.

Placenta praevia contributes to The Development of Amniotic Fluid Embolism. As a result of impaired Blood Coagulation properties, Fibrinolysis develops.

The complicated course of pregnancy and labor, the exclusion of a portion of the placenta from Circulation due to hemorrhage, and various surgical interventions all lead to Fetal Hypoxia, asphyxia, and birth trauma in the newborn.

Diagnosis of placenta praevia is performed using external and internal examination Methods. A high standing of the presenting fetal part indicates the presence of placenta praevia. A vaginal examination should be performed with a prepared operating room, very carefully and cautiously. To identify the source of bleeding, it is necessary to inspect the cervix and Vagina using specula to rule out polyps, Cervical Cancer, or a ruptured varicose vein.

The degree of placenta praevia is established during a vaginal examination when the cervical dilation is at least 4–6 cm. In complete placenta praevia, the membranes of the amniotic sac cannot be felt, whereas in incomplete praevia, they are palpated alongside the placenta. In some cases, one type of placenta praevia may transition into another.

Auscultation over the lower uterine segment reveals the sound of placental vessels.

An objective and harmless method for diagnosing placenta praevia is Ultrasound examination (Ultrasonography), which makes it possible to determine the localization of the placenta. It is advisable to perform serial ultrasound scans (at 16, 25–26, and 34–36 weeks of gestation). Before ultrasound became standard practice in obstetrics for diagnosing placenta praevia, Instrumental Diagnostic Methods were used: cystography (which reveals an increased space between the Urinary Bladder and the fetal head) and placentography (the Introduction of contrast agents into the bloodstream that accumulate in the placental vessels). However, these methods are hazardous and are therefore no longer used. A pregnant woman presenting with Complaints of spotting or bleeding must be hospitalized.

Treatment and evaluation of pregnant women with bleeding in the second half of pregnancy must be carried out exclusively in a hospital Setting. The choice of treatment and its timing depend on the type of placenta praevia, the intensity of the bleeding, the condition of the birth canal, and the General condition of the mother and fetus. Conservative management is indicated for preterm pregnancies with minor bleeding that does not cause pronounced anemia, provided the woman's condition is satisfactory. Strict bed rest is prescribed, along with repeated transfusions of small blood volumes, tocolytic and antispasmodic agents, and anti-anemic drugs that normalize uteroplacental circulation, strengthen vascular walls, and enhance blood clotting. Sedatives (valerian ROOT, motherwort herb, seduxen) may also be administered. Prevention of endometritis and fetal hypoxia is actively carried out.

Laxatives are strictly contraindicated for pregnant women with placenta praevia. When necessary, a cleansing enema is administered.

To promote placental migration, a cervical cerclage (purse-string suture) may be placed at the level of the internal os between 20 and 28 weeks of gestation.

Indications for a Cesarean Section in cases of placenta praevia include:

— complete placenta praevia at 38 weeks of gestation;

— a single blood loss of 250 ml or more with ongoing hemorrhage;

— recurrent hemorrhages exceeding a volume of 200 ml;

— combination of mild blood loss with anemia and hypotension;

— hemorrhage in partial placenta previa combined with other obstetric and somatic pathologies.

In such cases, the surgery is performed according to maternal vital indications, regardless of the gestational age and fetal condition.

In cases of partial placenta previa and minor bleeding during labor, delivery via the natural birth canal is possible. To reduce or stop the bleeding, Amniotomy (rupture of the fetal membranes) is performed, which halts further placental detachment, while the presenting part of the fetus descends and compresses the placenta against the uterine wall. If this Procedure proves ineffective and the fetus is non-viable, scalp traction can be applied using Willet-&-Ivanov double-tooth forceps, with a 300–400 g weight attached to the handle; this causes the head to descend and press the placenta against the uterine wall, thereby arresting the hemorrhage. In the presence of a mixed breech presentation with sufficient cervical dilation (6–10 cm), bringing down a fetal FOOT is an option, which presses the placenta against the uterine wall and stops the bleeding. Currently, these Procedures are rarely performed, mainly in cases of a non-viable fetus. If the aforementioned methods fail and labor activity is absent, a Cesarean section is performed.

Cesarean section is also indicated when placenta previa is combined with other obstetric complications, even in the presence of moderate bleeding (abnormal fetal presentation, elderly primigravida, contracted pelvis, etc.).

Conservative Management of Labor is feasible in partial placenta previa provided that the bleeding ceases after amniotomy. Amniotomy is performed during active labor with a cervical dilation of 5–6 cm, matching dimensions of the fetal head and maternal pelvis, vertex presentation, and absence of Uterine Contractile Dysfunction.

The principles of conservative labor management include: early amniotomy with prior administration of spasmolytics (No-spa, papaverine, baralgin); intravenous administration of spasmolytics During the first stage of labor; readiness for infusion therapy; manual removal of the placenta with inspection of the uterine cavity integrity; prevention of hypotonic hemorrhage via uterotonics (methylergometrine, oxytocin, etc.); and if bleeding persists, laparotomy and Hysterectomy are indicated.

Discharge of pregnant women with placenta previa is carried out exclusively postpartum.

The prognosis for the patient is quite serious. With timely medical care, the risk is significantly reduced, and the majority of postpartum women make a full recovery while retaining their working capacity and the functional integrity of the Reproductive System.

Prevention of placenta previa is aimed at combating induced abortions, as well as preventing and timely treating inflammatory conditions of the reproductive Organs.