Educational clinical resource
Placenta previa and placenta accreta spectrum
Placenta location, previous uterine surgery, ultrasound signs, bleeding, and delivery resources determine the care pathway for previa and accreta risk.
- 01Maternal health
- 02Placenta
- 03Fetal growth
- 04Preterm birth risk
How to navigate Placenta previa and placenta accreta spectrum
An educational path from the first question to the next step. It does not replace individual assessment.
- 01Recognise the finding
Name the maternal, fetal, placental, or pregnancy concern precisely.
- 02Confirm what it means
Check gestation, diagnostic criteria, severity, and possible alternatives.
- 03Stratify risk
Identify what changes maternal safety, fetal wellbeing, timing, or prognosis.
- 04Plan surveillance
Match monitoring intensity to the condition and how quickly it can change.
- 05Escalate when needed
Refer, admit, treat, or plan birth when thresholds are reached.
Visual decision pathway
Low placenta to prepared delivery pathway
Placental position alone is not the endpoint; uterine scars, imaging signs, bleeding and hospital capability define the route.
- MapConfirm placental position
Define the relationship to cervix, scar, uterine wall and bladder.
- RiskEstimate accreta probability
Combine previous uterine surgery with targeted grayscale and Doppler findings.
- ProtectCreate a bleeding plan
Specify emergency destination, contact, transport and transfusion readiness.
- PreparePlan multidisciplinary delivery
Match timing, surgical team, anaesthesia, blood bank, critical care and neonatal support.
Placenta previa means the placenta lies over or very close to the cervix. Placenta accreta spectrum describes abnormal attachment of the placenta into the uterine wall, which can prevent normal separation after birth and cause life-threatening bleeding. They are related but not interchangeable diagnoses.
Why previous cesarean birth matters
The risk of placenta accreta spectrum rises when a low-lying placenta or previa overlies a previous uterine scar, and it increases with the number of previous cesarean births. Other uterine surgery can also matter. A history-based risk assessment should therefore be combined with targeted ultrasound rather than relying on placental position alone.
What ultrasound looks for
Specialist ultrasound evaluates the relationship between placenta, cervix, bladder, uterine wall, and previous scar, using grayscale and Doppler findings. MRI can help in selected cases but does not replace expert ultrasound as the primary assessment. Diagnostic language should communicate the level of suspicion because certainty may remain limited before surgery.
Bleeding is an emergency signal
Any vaginal bleeding in a pregnancy known or suspected to have placenta previa requires prompt assessment. Heavy bleeding, faintness, severe pain, contractions, or reduced fetal movements requires emergency care. Patients should know which hospital to attend, whom to call, and what travel or transfer time means for the plan.
Why planned delivery matters
When accreta is suspected, outcomes are improved by recognition before labour or major bleeding and by delivery in a prepared multidisciplinary setting. Planning may involve maternal–fetal medicine, experienced obstetric and pelvic surgeons, anaesthesia, blood bank and massive-transfusion capability, interventional services where appropriate, critical care, neonatology, and a rehearsed operating plan.
The safest plan is not defined by a single scan label. It is defined by the probability and extent of invasion, bleeding history, gestational age, maternal condition, fetal status, and the real capabilities of the delivery hospital.