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Risk factors. Risks in placenta previa. Management
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Risk factors
Placenta praevia is associated with a number of risk factors, including:
· previous placenta praevia
· previous Caesarean section
· increased maternal age
· increased parity
· history of intrauterine procedures (D& C, etc. )
· previous endometritis
· large placentas:
o multiple gestations
o erythroblastosis
· maternal history of smoking
Clinical Picture
The main sign of placenta praevia is vaginal bleeding. In the central placenta praevia bleeding begins during the last two or three months of pregnancy; in the lateral attachment bleeding begins at the end of pregnancy or at the beginning of labor, and in the marginal placenta praevia, during the first stage of labor. In low attachment type of placenta praevia bleeding also begins during the dilation stage and is usually not pronounced.
Bleeding in late pregnancy usually begins unexpectedly, without any visible cause, sometimes during night rest. The bleeding is painless; sometimes it appears as lengthy smearing, and sometimes as a single bloody discharge (with clots) followed by cessation of bleeding and unwarned recurrence in an uncertain lapse of time. Intermittent bleeding may persist till labor. Bleeding is sometimes rather intense and urgent labor is then indicated.
In central placenta praevia bleeding intensifies with the onset of regular contractions; the blood is bright and liquid, sometimes containing clots; it is discharged in large portions or continuously. The blood loss may amount to one litre and over, and the bleeding may become fatal provided the patient is not given timely aid. If bleeding in lateral placenta praevia begins during pregnancy, it intensifies during labor as well and its character may become fatal. Bleeding is not usually dangerous in marginal placenta previa; it begins during the dilation stage of labor. When the membranes rupture, the separation of the placenta discontinues, the head becomes engaged in the pelvis to compress the placenta, and the bleeding thus stops.
A pronounced symptom of placenta praevia is anemia, the degree of which depends on the intensity of the vaginal bleeding. The skin and the mucosa turn pale, the pulse accelerates; if the bleeding is excessive, the arterial pressure falls, vertigo, noise in the ears and dimness in the eyes develop, and the woman may die should the medical aid be delayed.
Placenta praevia interferes with the descent of the head into the lower uterine segment. The head therefore remains floated high above the pelvic inlet till the end of pregnancy or it may deviate to the either side of the vertical line. Placenta praevia contributes to the incidence of abnormal presentations (breech, oblique, transverse). Premature labor, uterine inertia, intrauterine fetal hypoxia and hypotrophy are not infrequent.
Risks in placenta previa
Risks for mother:
- hemorrhages
- anemia
- complications of surgery,
- postpartum sepsis
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Risks for fetus:
- preterm birth,
- intrauterine distress,
- intrauterine growth restriction,
- deflexed cephalic presentations,
- breech presentations
- transverse/oblique lying
- intrauterine death
Diagnosis
Late pregnancy bleeding, as well as bleeding during the first stage of labor, is the main sign of placenta praevia. Painless bleeding without warning and in the absence of trauma is in most cases caused by placenta praevia. A high level of the presenting part in a normal bony pelvis confirms a suspected diagnosis.
Ultrasonography is the best way to distinguish placenta praevia.
Vaginal examination is contraindicated in central or lateral placenta praevia, in which it precipitates greater hemorrhage.
Vaginal examination may be performed in a hospital with a strict observation of the aseptic requirements, with patient and surgeon being prepared for operation. When the cervix opens, soft tissue can be palpated by the examining finger in the immediate vicinity of the internal os margin; in partial placenta praevia, the membranes can be palpated together with the placenta through the cervix. The examining finger should not reach beyond the margin of the internal os because this may intensify the separation of the placenta and bleeding.
In order to establish a definite diagnosis and to rule out other sources of bleeding (cancer, polyps, rupture of varicose veins, trauma) the woman with bleeding should undergo a specular examination.
Management
If placenta previa is suspected, the pregnant woman must be hospitalized necessarily. The goals of the treatment are to stop the bleeding, if any, and to prevent bleeding, provide symptomatic treatment and prepare the patient for delivery (choice of time and mode of delivery). Management depends on:
• the grade of the placenta previa,
• the term of pregnancy or stage of labor,
• the fetus condition,
• and most importantly – the rate of bleeding and the amount of blood lost.
Expected management and emergency cessation of pregnancy in cesarean section (CS) are commonly used for management of placenta previaIndications for expectant management.
Expectant management may be provided if:
• no indications for urgent termination of pregnancy
- vaginal bleeding is insignificant;
- patient condition is stable (mean arterial blood pressure (MAP) > 100 mm Hg, Hb ≥ 100 g/l);
• < 36 weeks gestation;
• fetal weight < 2300g.
In other cases, emergent surgical intervention is indicated.
Placenta previa without clinical manifestations is not an absolute indication for hospitalization (if a woman refuses), the main rule is not to remain alone and out of reach of the medical institution.
The most suitable method of treatment should be selected in each particular case, taking into consideration the following factors: the amount of blood discharge, the degree of anemia developed, preparedness of the birth canal for delivery, and the status of the fetus (asphyxia, etc). Depending on these factors some women may be treated conservatively, while others should immediately be given an urgent surgical aid, including a cesarean section.
Strict bed rest, tocolytic treatment to reduce uterine contractions/irritability, symptomatic medications are indicated. In case of premature pregnancy (up to 34 weeks), corticosteroids to improve lung surfactant development should be administered. In preterm pregnancy if no vaginal bleeding and the general condition of both mother and her fetus are satisfactory, the patient can be discharged under the out – patient supervision.
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Indications for surgical intervention at any term of pregnancy with placenta previa are:
• profuse bleeding (with profuse instant bleeding in a volume of 250 ml or more, regardless of the grade of the placenta previa and the gestational age, an emergency cesarean section is absolutely indicated),
• acute fetal distress
• anemia in the expectant mother.
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Bleeding in total placenta previa is an absolute indication for cesarean section regardless of the gestational age.
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