ACR Appropriateness Criteria®
Clinical Condition: Second and Third Trimester Vaginal Bleeding
Variant 1: No other signs or symptoms.
Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
US, pregnant, uterus, transabdominal (TA) |
9 |
|
US, pregnant, uterus, transperineal |
8 |
|
US, pregnant, uterus, transperineal |
6 |
|
MRI, pelvis |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Internal cervical os not visible by transabdominal ultrasound.
Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
US, pregnant, uterus, transperineal |
9 |
|
US, pregnant, uterus, transvaginal |
8 |
|
US, pregnant, uterus, repeat TA |
4 |
|
MRI, pelvis |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 3: Placenta previa diagnosed before 32 weeks.
Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
US, pregnant, uterus, 32-34 weeks |
8 |
|
US, pregnant, uterus, once per month |
4 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Vaginal bleeding after the first trimester of pregnancy and before term may be due to premature delivery, placenta previa, placental abruption, placenta accreta or its variants, or of unknown origin. Placenta previa can be excluded if the placenta is shown to lie away from the internal os of the cervix, which can almost always be accomplished by transabdominal ultrasound examination of the cervix and lower uterine segment with the bladder full. If the anatomy is obscured by the fetal head, by hematoma, by a suspected lower uterine segment contraction, or by an overly full bladder, transperineal scanning or more commonly transvaginal scanning with the bladder empty will almost always result in the correct diagnosis. MRI has been suggested as an alternative to transvaginal or transperineal scanning if ultrasound is inconclusive; however, MRI is rarely needed.
Placenta previa diagnosed in the second trimester may not persist until term because of growth of the lower uterine segment. One should avoid the use of terms such as "low-lying placenta," "marginal previa," "total previa," or "complete previa" since these terms are vague and difficult to quantify. It is better to describe the relationship of the inferior placenta to the internal cervical os in centimeters. If a placenta extends to, or partially covers, the internal os of the cervix before 28 weeks gestation, there is a 4% to 5% chance it will persist in this abnormal location until term, as compared to more than a 50% chance if it completely covers the os at 28 weeks. At any point in gestation if the placenta covers the cervix and is fully implanted on both the anterior and posterior walls of the lower uterine segment, placenta location is unlikely to change.
Placental abruption can be imaged by ultrasound. However, the echogenicity of clot and the echogenicity of placenta can be similar, and therefore a normal exam does not exclude abruption. In general, in a patient with second or third trimester bleeding, in the absence of diagnosis of placenta previa by ultrasound, the management of the pregnancy depends on the clinical circumstances. If clinical circumstances or ultrasound findings are confusing, MRI may help better define the location of the placenta and the presence of abruption
Abbreviations
- MRI, magnetic resonance imaging
- TA, transabdominal
- US, ultrasound