A placenta that ends within 2 cm of the internal cervical os but that is not abutting the internal os is known as a low-lying placenta. Patients with a low-lying placenta are at increased risk for antepartum hemorrhage and cesarean delivery, although descent of the fetal head in labor often tamponades any intrapartum bleeding that may occur.

• A vaginal delivery is successful in 43% of patients with a placenta that is within 10 mm of the internal cervical os.

  • Patients with a placenta within 10 mm of the internal cervical os may be allowed to labor but should be counseled about the increased risk for cesarean delivery and bleeding.

  • Excellent intravenous access and blood type and screen are necessary for these patients.

• Patients whose placental end is 11 to 20 mm from the internal cervical os have an 85% rate of successful vaginal delivery, similar to that of patients whose placenta ends >20 mm from the internal cervical os.