Teaching File- What is so Important about the Central Type of Complete Previa
Take Home Points
What is a complete "central" previa?
- Complete Previa: The placenta completely covers the internal cervical os
- Complete Central Previa: The bulk of the placenta is centered on the internal os (This is an important distinction)
- Of note: Recently, a consensus panel removed the terms "complete" and "marginal" previa.
- What was previously termed complete previa, they proposed to call just a previa
- What was termed marginal previa (where placenta does not cover the internal os) as just low lying placenta, even if the placenta inserts onto the cervical stroma.
what is the unique implication of a central previa
- The placenta covering the internal os, can abrupt and infarct and thus appear to "regress"
- You essentially can end up with a "donut" placenta that has a hole in the middle, overlying the cervix.
- On imaging, it will look as if there is no placenta covering the internal os, however the membrane of the placenta containing fetal vessels is still there.
- Thus, there is now a vasa previa which is equally or more dangerous of a situation. Check out this video (click here) to learn more about vasa previa
when in doubt, "drop a dop"
- Any time you see a "solid appearing mass," interogate it with Doppler. In this case, there was a "mass" in the vaginal canal. There was no flow in it with Doppler, confirming the suspicion that it was clot
relative contraindications to endovaginal imaging
- We usually like to interrogate placenta previa with Doppler imaging to better characterize, however if there is significant active bleeding, this is a general contraindication to endovaginal scanning.
- Obviously there is a spectrum to what is considered "significant" bleeding, so if you are unsure, make sure to engage the patient's primary physician to help make the decision.
- The other main contraindication is: Premature Rupture of Membranes due to the risk of infection