Placenta Praevia, Accreta and Vasa Praevia: What Is the Difference?
Key message: These are different conditions linked by the importance of placental or vessel position. Accurate ultrasound and…
Key message: These are different conditions linked by the importance of placental or vessel position. Accurate ultrasound and planned birth in an appropriate centre reduce the chance of unexpected bleeding and emergency delivery.
Get urgent help: Any bleeding in the second half of pregnancy needs urgent maternity advice even if it stops. Call emergency services for heavy bleeding, dizziness or collapse. Contractions, pain or waters breaking with placenta or vasa praevia also require immediate hospital care.
What is a low-lying placenta or placenta praevia?
A low-lying placenta is close to the cervix; placenta praevia covers the cervical opening later in pregnancy and may prevent safe vaginal birth.
Many placentas described as low at the anomaly scan move relatively away as the uterus grows, so repeat scanning is important.
What is placenta accreta spectrum?
The placenta attaches abnormally deeply into the uterine wall and may not separate normally after birth. Previous caesarean plus a low placenta is a major risk factor.
Severity varies, and final diagnosis may only be completely clear during surgery or after pathology.
What is vasa praevia?
Unprotected fetal blood vessels run through the membranes close to the cervix. If they tear when labour starts or waters break, the baby can lose blood rapidly.
It is rare but requires a planned caesarean before labour or membrane rupture when diagnosed.
How are they diagnosed?
- Repeat transvaginal ultrasound for placental distance; this is generally safe and most accurate.
- Colour Doppler to identify fetal vessels and placental cord insertion.
- Specialist ultrasound for signs of accreta.
- MRI in selected accreta cases for surgical planning, not automatically for everyone.
- Review of previous caesareans, uterine surgery and bleeding.
How is placenta praevia managed?
Persistent placenta praevia usually requires planned caesarean before labour. Timing depends on bleeding, placenta position and other findings.
Recurrent bleeding may require hospital admission, blood preparation or earlier birth. Avoid vaginal examination outside an appropriate setting when praevia is suspected.
How is suspected accreta managed?
Birth is planned with a multidisciplinary team in a centre able to manage major haemorrhage, transfusion, critical care and neonatal needs. The placenta is often left in place and hysterectomy may be required to control life-threatening bleeding.
The surgical and fertility consequences should be discussed before birth.
How is vasa praevia managed?
A planned caesarean is arranged before labour and waters breaking. Corticosteroids, admission and timing are individualised according to gestation, symptoms, cervical length and local expertise.
Bleeding or rupture of membranes can require immediate emergency birth.
What preparation supports safety?
- Treat anaemia and document blood group and antibodies.
- Plan the birth hospital, timing, surgical team and blood products.
- Carry written instructions for bleeding.
- Discuss corticosteroids when preterm birth is likely.
- Arrange neonatal, intensive-care and psychological support when relevant.
Frequently asked questions
Will a low placenta at 20 weeks stay low?
Not necessarily. Many move away from the cervix and need a later scan.
Is transvaginal ultrasound safe with a low placenta?
When performed correctly it is generally safe and gives the most accurate measurement.
Does accreta always require hysterectomy?
Not always, but hysterectomy is often the safest life-saving plan when significant accreta is suspected.
Can vasa praevia cause maternal bleeding?
The dangerous bleeding comes from fetal vessels, which is why rupture is an emergency.
Can I deliver vaginally with placenta praevia?
A placenta covering the cervix usually requires caesarean; a low placenta is assessed by exact distance and circumstances.
Your next step
Keep the latest placental report with you and know the designated hospital. Any bleeding, waters breaking or labour symptoms require immediate maternity contact.
Medical and content review: Dr Mohamed Abdelghany, Obstetrics & Gynecology Specialist, MRCOG (UK), MSc Obstetrics & Gynecology – Kasr Al-Ainy, Cairo University.
Last reviewed: 23 August 2026.
This information is for general education and does not replace individual medical assessment. Severe, sudden or concerning symptoms should not wait for a routine appointment.
