Several. Placental location, placental depth of penetration into the wall with certain abnormal conditions. Where and how the cord inserts in the placenta can be important at times. With twins or multiples gestations, there are a number of important factors looked for by ultrasound, including blood vessel communication and comparison of sizes. Nmber of blood vessels in the umbilical cord can also value.
Many. Abnormal position over cervix: previa masses: chorionagioma fluid: placental lakes: these are of no clinical significance, although something called a subchorial plate hematoma is important. Bleeding: placental abruption invasion: placenta accreta.