Ultrasound can sometimes show placental abruption, which happens when the placenta starts to separate from the wall of the uterus before birth. The scan may reveal a collection of blood near or behind the placenta or an unusual-looking placenta. However, a normal ultrasound does not rule out abruption. Clinicians also consider symptoms, examination findings, pregnancy stage, and the baby’s heart rate.
What can placental abruption look like on ultrasound?
Placental abruption occurs when the placenta separates partly or completely from the uterine wall before the baby is born. This separation can cause blood to collect between the placenta and the uterus or in nearby areas. Ultrasound may show these blood collections, sometimes called hematomas, along with changes in the appearance of the placenta.
According to the Cleveland Clinic, placental abruption can affect the transfer of oxygen and nutrients to the baby and may cause bleeding. An ultrasound can help clinicians examine the placenta and look for signs of bleeding, but the findings need to be interpreted alongside the overall pregnancy assessment.
Which ultrasound findings may suggest placental abruption?
The appearance depends on where the bleeding occurs, how much blood collects, and how much time has passed since the separation began. A scan may show one or more findings that raise concern for placental abruption.
- A collection of blood behind the placenta: Blood may collect between the placenta and the uterine wall. This is called a retroplacental hematoma.
- A collection near the edge of the placenta: Bleeding may occur along the placental margin or beneath the membranes surrounding the pregnancy.
- Changes in placental thickness: The placenta may appear thicker than expected in some cases, particularly when blood is difficult to distinguish from the placental tissue itself.
- An uneven or mixed appearance: The placenta may have areas with different ultrasound appearances rather than a uniform texture.
- Blood within or near the amniotic sac: In some cases, ultrasound may identify blood or a blood collection within the amniotic cavity.
A 2023 imaging review available through the U.S. National Library of Medicine's PubMed Central describes these varied ultrasound appearances, including blood collections near or within the placenta and changes in placental thickness or texture. No single finding appears in every case, so the absence of one particular feature does not exclude placental abruption.
Can an ultrasound miss placental abruption?
Yes. Ultrasound does not detect every placental abruption, and a normal scan cannot reliably exclude the condition when other clinical findings raise concern. Fresh blood may have a similar appearance to the surrounding placental tissue, making it difficult to identify. Small collections may also be hard to see, and the appearance of a hematoma can change as the blood changes over time.
The Merck Manual Professional Edition explains that ultrasound may reveal some cases of placental abruption, but normal findings can occur even when an abruption is present. For this reason, healthcare professionals do not rely on ultrasound alone to decide whether the condition is present.
A scan result must therefore be considered in context. For example, a reassuring ultrasound does not remove the need for urgent assessment if a pregnant person has new vaginal bleeding, ongoing abdominal pain, uterine tenderness, or other concerning changes. Clinical assessment remains important even when the imaging report does not identify a clear abnormality.
What does a placental ultrasound report mean?
An ultrasound report may describe the location and appearance of the placenta, the presence or absence of a visible blood collection, and any other findings that need follow-up. Terms such as "retroplacental collection," "subchorionic hematoma," "placental thickening," or "heterogeneous placental appearance" describe imaging features. Their significance depends on the location and appearance of the finding, the stage of pregnancy, and the clinical situation.
A report that mentions a hematoma does not automatically establish that a clinically significant placental abruption has occurred. Conversely, a report stating that the placenta looks normal cannot, by itself, exclude abruption. The clinician interpreting the report will consider whether the findings fit the symptoms and examination, as well as whether other explanations need to be considered.
What other tests are used when abruption is suspected?
When placental abruption is a concern, the care team assesses the health of the pregnant person and the baby rather than relying on a picture of the placenta alone. The evaluation may include:
- Clinical assessment: The care team asks about bleeding, pain, contractions, when symptoms began, and any recent abdominal injury. Blood pressure and other vital signs may also be checked.
- Fetal heart rate monitoring: Monitoring helps assess the baby's heart rate and identify patterns that may indicate the baby is not receiving enough oxygen.
- Blood tests: Depending on the situation, tests may assess blood loss, blood group, and the blood's ability to clot.
- Ultrasound examination: Imaging helps assess placental location, look for visible blood collections, and check relevant aspects of the pregnancy.
MedlinePlus notes that clinicians may use ultrasound to examine the placenta but that the scan does not always show an abruption. Checking the baby's heart rate is also an important part of the assessment when this complication is suspected.
The need for hospital observation, repeat imaging, or delivery depends on the findings as a whole. Gestational age, the mother's condition, ongoing bleeding, and the baby's heart rate can all influence decisions. A repeat ultrasound may help clinicians follow a visible collection in selected situations, but care should not be delayed while waiting for another scan when urgent concerns are present.
When should you seek urgent medical assessment?
Placental abruption can become an obstetric emergency because bleeding may affect the pregnant person and reduce the baby's oxygen supply. Bleeding can sometimes remain trapped behind the placenta, so the amount of visible vaginal blood does not always reflect what is happening internally.
If you are pregnant and experience any of the following, contact your maternity unit or seek emergency medical assessment immediately rather than waiting for a scheduled ultrasound:
- Vaginal bleeding during pregnancy.
- New, persistent, or sudden abdominal or back pain.
- Unusual or painful tightening of the uterus or repeated contractions.
- Noticeably reduced fetal movement compared with your baby's usual pattern.
- Abdominal pain or bleeding following a fall, collision, or blow to the abdomen.
- Significant weakness, dizziness, fainting, or other signs that may accompany substantial blood loss.
These experiences can have different causes, but they need prompt evaluation during pregnancy. If symptoms are significant or you feel faint or unwell, use emergency services rather than attempting to travel alone.
Can a normal ultrasound provide reassurance?
A normal ultrasound can provide useful information about the placenta and the baby, but it does not completely rule out placental abruption. When there are no concerning symptoms and the overall assessment is reassuring, the findings may be reassuring to the care team. When symptoms or monitoring results remain concerning, further assessment may still be needed even if the scan looks normal.
The most important point is that ultrasound is one part of the evaluation, not a stand-alone test for placental abruption. Prompt communication with the pregnancy care team helps ensure that imaging findings, symptoms, examination results, and fetal monitoring are considered together.