Placenta previa, placenta accreta, and vasa previa

Placenta previa, placenta accreta, and vasa previa are important causes of bleeding in the second half of pregnancy and in labor. Risk factors for placenta previa include prior cesarean delivery, pregnancy termination, intrauterine surgery, smoking, multifetal gestation, increasing parity, and maternal age. The diagnostic modality of choice for placenta previa is transvaginal ultrasonography, and women with a complete placenta previa should be delivered by cesarean. Small studies suggest that, when the placenta to cervical os distance is greater than 2 cm, women may safely have a vaginal delivery. Regional anesthesia for cesarean delivery in women with placenta previa is safe. Delivery should take place at an institution with adequate blood banking facilities. The incidence of placenta accreta is rising, primarily because of the rise in cesarean delivery rates. This condition can be associated with massive blood loss at delivery. Prenatal diagnosis by imaging, followed by planning of peripartum management by a multidisciplinary team, may help reduce morbidity and mortality. Women known to have placenta accreta should be delivered by cesarean, and no attempt should be made to separate the placenta at the time of delivery. The majority of women with significant degrees of placenta accreta will require a hysterectomy. Although successful conservative management has been described, there are currently insufficient data to recommend this approach to management routinely. Vasa previa carries a risk of fetal exsanguination and death when the membranes rupture. The condition can be diagnosed prenatally by ultrasound examination. Good outcomes depend on prenatal diagnosis and cesarean delivery before the membranes rupture.     

Placenta previa/accreta and prior cesarean section

To assess the relationship between increasing numbers of previous cesarean sections and the subsequent development of placenta previa and placenta accreta, the records of all patients presenting to labor and delivery with the diagnosis of placenta previa between 1977 and 1983 were examined. Of a total of 97,799 patients, 292 (0.3%) had a placenta previa. The risk of placenta previa was 0.26% with an unscarred uterus and increased almost linearly with the number of prior cesarean sections to 10% in patients with four or more. The effect of advancing age and parity on the incidence of placenta previa was much less dramatic. Patients presenting with a placenta previa and an unscarred uterus had a 5% risk of clinical placenta accreta. With a placenta previa and one previous cesarean section, the risk of placenta accreta was 24%; this risk continued to increase to 67% (two of three) with a placenta previa and four or more cesarean sections. Possible mechanisms and clinical implications are discussed.     

Placenta previa and accreta complicated by amniotic fluid embolism

BACKGROUND: The simultaneous occurrence of placenta previa and placenta accreta in patients who had previous low transverse cesarean delivery is presently well established. However, the sequence of previous cesarean delivery followed by placenta previa and accreta in a patient who also experiences a premature rupture of membranes as well as amniotic fluid embolism (AFE) is a rare obstetric phenomenon. CASE: A 24-year-old woman, para 2 with two previous cesarean deliveries, at 32 weeks' gestation by last menstrual period, was admitted with premature rupture of membranes. A repeat cesarean delivery (CD) was done. Excessive hemorrhage occurred, necessitating a hysterectomy. Also, the patient developed an amniotic fluid embolism. CONCLUSION: Placenta previa and placenta accreta may be observed in patients who have a previous CD scar and in whom AFE develops suddenly and unexpectedly. AFE, a condition with complex pathogenesis, presents a number of challenges, with the patient undergoing serious complications that may include massive hemorrhage, disseminated intravascular coagulopathy, and death. The obstetrician should be alert to the symptoms of AFE, and if they occur should begin prompt and aggressive treatment.     

Placenta membranacea, previa and accreta. A case report.

A case of placenta membranacea, previa and accreta was managed conservatively and resulted in delivery of a mature fetus. The diagnosis of placenta membranacea and previa was obtained with ultrasound. The placenta previa and accreta necessitated a cesarean delivery and hysterectomy.     

Placenta previa

A placenta previa, whether found fortuitously by ultrasound or with the clinical emergency of maternal hemorrhage, carries significant maternal and fetal risk. Accurate diagnosis, judicious expectant management with transfusion as required, and delivery at the time of fetal lung maturation can lead to the most favorable outcome. Anticipation of the clinical complication of placenta accreta may avoid some serious consequences. Clinical judgement and skill in the performance of cesarean sections, dilatation and curettage, and other forms of uterine invasive techniques may help to keep subsequent incidence of placenta previa at a reasonably low rate.