Does Ultrasound have a role in assessing second and third trimester maternal pain and bleeding?
The major consideration in any pregnant patient presenting with pelvic pain or bleeding is placental hemorrhage and placental abruption. Risk factors for placental hemorrhage include maternal hypertension, smoking, alcohol or cocaine use, trauma, and premature rupture of membranes. The role of US is to detect hemorrhage/hematoma associated with the placenta. Hemorrhage is describe as retroplacental if it is located between the placenta and uterine wall, marginal if it is located lateral to the placenta, and intraplacental if it is located within the placenta. Placental abruption occurs if a retroplacental hemorrhage is large enough to separate the placenta from the uterus.
Placental bleeds can be difficult to detect sonographically if the blood readily decompresses through the vagina rather than building up as a measurable hematoma. Visualization of a retroplacental hematoma on US is associated with a worse outcome for the fetus and mother due to a higher risk of complete placental separation. Depending on the age of the placental bleed, the blood products may range from hypoechoic or completely anechoic in the acute and chronic phases to hyperechoic and heterogeneous in the subacute phase.