The ultrasound shows a complete placenta previa (Figure), an implantation of the placenta over the lower part of the uterus covering all of the internal cervical os. Placenta previa occurs in 0.3% to 0.5% of all pregnancies,1 and most cases are diagnosed in asymptomatic women during routine ultrasonography in the second trimester. There are 4 types of placenta previa defined according to the relationship of the placenta to the internal os: complete, partial, marginal, and low-lying. A complete or partial placenta previa requires cesarean delivery. Immediate cesarean delivery in these patients is indicated if there is significant bleeding after 34 weeks of gestation; there are nonreassuring fetal heart tracings despite oxygen, IV fluids, and maternal positioning to the left side; and maternal cardiovascular status cannot be stabilized.1 Women with a complete or partial placenta previa should be admitted for continued maternal and fetal monitoring, even if bleeding has stopped. Asymptomatic patients (no bleeding or spotting) with a complete or partial placenta previa can be managed on an outpatient basis with serial ultrasound, abstaining from sexual intercourse, and avoidance of digital pelvic examinations; delivery is by scheduled cesarean section.1 Symptomatic patients (currently bleeding or history of bleeding that has stopped) are admitted for fetal and maternal monitoring. Patients with marginal or low-lying placenta are managed similarly to those with complete or partial placenta previa. However, the mode of delivery for these patients is controversial (vaginal versus caesarean delivery) and left to the discretion of the attending obstetrician.1
- Placenta previa.
1. Oyelese Y, Smulian JC. Placenta previa, placenta accreta, and vasa previa. Obstet Gynecol 2006;107:927–41.
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