A woman with a documented type IV vasa previa on antenatal ultrasound is scheduled for cesarean delivery. The SMFM definition of vasa previa type II specifically refers to:

• A Velamentous cord insertion with fetal vessels over the internal os
• B Fetal vessels traversing a succenturiate lobe placenta over the lower segment ✓
• C Bilobed placenta with vessels connecting the two lobes over the cervix
• D Circumvallate placenta with eccentric cord insertion

Explanation

Vasa previa type I involves velamentous cord insertion where unprotected fetal vessels overlie the internal cervical os. Type II involves fetal vessels connecting a main placenta to a succenturiate (accessory) lobe traversing over the internal os. Both types carry risk of fetal hemorrhage if membranes rupture. Type II is particularly subtle on imaging because the vessels are between two placental masses rather than near the cord insertion. Antenatal diagnosis by transvaginal color Doppler is critical; elective cesarean before labor is recommended at 34–35 weeks.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.