Placenta previa is a complication of pregnancy where the placenta is partially or fully covering the opening of the uterus. It is the most common cause of painless bleeding in pregnancy and can have varied outcomes in pregnancy and mode of delivery depending on its severity.

There are 4 grades of placenta previa:

• Grade 1 (minor) Placenta is low-lying but does not cover the internal opening
• Grade 2 (marginal) Placental edge is reaching the internal opening
• Grade 3 (partial) Lower placental edge partially covering the internal opening
• Grade 4 (complete) Placenta is completely covering the internal opening

Sometimes Grade 1 or 2 placenta previa can resolve during pregnancy as your uterus expands and moves. This is because the site where your placenta attaches usually stretches upwards as the pregnancy progresses.

The position of your placenta will be checked at your 18-22 week ultrasound. If your placenta is low-lying at this scan, you will be offered additional ultrasound scanning throughout your pregnancy to monitor its position.

What does placenta previa mean for your pregnancy?

If you have placenta previa, your baby may need to be monitored frequently during your pregnancy. This may mean more regular scans, blood tests and cardiotocography (CTG) monitoring. This is when your baby’s heartrate is recorded on a continuous trace for short periods of time to assess wellbeing.

If you experience light bleeding during your pregnancy due to placenta previa you may need to be admitted to hospital for intermittent monitoring or in some circumstances, admitted for monitoring until your delivery.

If you have heavy bleeding in your pregnancy you may need to have an emergency caesarean (even prematurely) as a lifesaving procedure.

What does placenta previa mean for your delivery?

If you have Grade 3 or 4 placenta previa after 32 weeks gestation, you will be advised to have an elective caesarean section when it comes to the right time. This is because the placenta is blocking your baby’s safe passage through the vaginal canal and vaginal birth carries significant risk of bleeding or fetal demise.

Timing of your caesarean will be impacted by several variables such as baby growth and wellbeing, your wellbeing, bleeding in pregnancy and its frequency/severity.

Placenta previa is associated with serious risk of complication and monitoring/awareness should not be disregarded. Serious complications can include:

• Haemorrhage (significant blood loss)
• Emergency Caesarean
• Premature delivery
• Negative infant outcomes
• Hysterectomy (removal of the uterus)

What causes placenta previa?

There are no recognised causes for placenta previa, however there are several risk factors that may increase your chances of having placenta previa:

• Twin pregnancy
• Advanced maternal age
• History of Caesarean section
• Smoking
• Breech presentation
• Unicornuate or Bicornuate uterus

If diagnosed, there is nothing you can do to resolve placenta previa on your own. It is important to receive routine antenatal care and scheduled ultrasound scanning to check the location of your placenta and its movement in your pregnancy.

Written by Keryn Thompson RM & IBCLC (L-301766)

References

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