Low-Lying Placenta vs. Placenta Praevia

In most pregnancies, the placenta attaches high up on the wall of the uterus. A low-lying placenta is the term used when the placenta attaches lower down, near or covering the cervix (the neck of the womb). This is a relatively common finding during the routine 18- to 22 week anatomy scan.

In the vast majority of cases, this condition resolves itself. As the uterus grows throughout the second and third trimesters, the placenta is carried upwards and away from the cervix. This process is often referred to as placental migration. 

Approximately 9 out of 10 people who have a low-lying placenta at 20 weeks will find that it has moved out of the way by the end of the pregnancy.

The term Placenta Praevia is used if the placenta remains low-lying after 20 weeks of pregnancy. This condition is defined by the placenta’s edge being less than 20 millimeters (mm) from the cervix, or completely covering it, at the later stages of pregnancy.

Only about 1 in 200 people will still have placenta praevia at the time of delivery.

Symptoms and Diagnosis : Placenta praevia is most often first suspected during the routine ultrasound scan. The most common symptom, if any occurs, is painless vaginal bleeding during the second or third trimester. This bleeding can range from light spotting to heavy blood loss and may sometimes occur after sexual intercourse.

Management and Follow-up : If a low-lying placenta is identified at 20-week scan,we recommend a follow-up plan to monitor the placenta’s position:

1. Follow-up Scan at 32 Weeks: which may include a transvaginal ultrasound for localisation of the placenta.

2. Further Scan at 36 Weeks: If the placenta is still low-lying at 32 weeks, a final scan will be offered at 36 weeks. The results of this scan are essential for planning the safest way for you to give birth.

3. Precautions: we may advise you to avoid sexual intercourse for the remainder of your pregnancy if bleeding exists.

4. Hospital Monitoring: may be necessary if there is active bleeding.

5. Steroid Injections: may be given to help mature the fetus’s lungs if there is a possibility of preterm birth.

Delivery Plan : The safest method of delivery is determined by the placenta’s position at the final 36-week scan.