What is placenta praevia? – This refers to a placenta that is located down the lower segment of the uterus, partially or completely covering the cervix (exit path for the baby), instead of the normal location at the upper part of the uterus. The placenta is the baby’s companion in the womb. It supplies the baby with blood through the umbilical cord.

What causes placenta praevia?

There is no known cause for placenta praevia but there are risk factors that increase the chance of having it:

1. Previous uterine surgery: caesarean section, fibroid surgery and dilatation and curettage.
2. More than four previous pregnancies
3. Cigarette smoking
4. Diabetes
5. Multiple pregnancy (twins, triplets etc.)
6. Age above 35 year
7. Anaemia (shortage of blood) in pregnancy

How is placenta praevia classified?

Placenta praevia is classified based on its relationship to the cervix.

1. Marginal placenta praevia: The edge of the placenta touches the edge of the cervix but does not cover it. As the pregnancy grows, the placenta may move up, away from the edge of the cervix. Repeat ultrasound scan may show the placenta at the normal location.
2. Partial placenta praevia: In this case, the placenta partially covers the cervix. Depending on the degree of coverage, this type may also move to the normal site before term.
3. Complete placenta praevia: Here, the placenta completely covers the cervix, blocking the passage of the baby out of the uterus. This type is unlikely to move to the normal location.

What are the symptoms of placenta praevia?

Placenta praevia may present with:

1. Vaginal bleeding: You may witness unprovoked bright red vaginal bleeding, which may be minimal or severe. This bleeding may occur many times during pregnancy, with the subsequent bleeding episodes usually worse than the previous ones.
2. No symptom: Occasionally, placenta praevia is present without vaginal bleeding but discovered incidentally during routine ultrasound scan.

In either of these scenarios, the diagnosis of placenta praevia can be made if your pregnancy is up to 28 weeks or above. Before this age, the placenta is described low-lying because the lower segment of the uterus is yet to develop. 

How is placenta praevia treated?

The treatment of placenta praevia is delivery by caesarean section.  However, before this, certain things are taken into consideration:

1. The age of the pregnancy (gestational age) – If the baby is already mature (gestational age more than 36 weeks), the recommended treatment option is delivery by caesarean section. If the fetus is premature (less than 36 weeks), the severity of the bleeding is considered.
2. No bleeding – In this case, you will be given shorter antenatal clinic appointment with serial ultrasound scan for monitoring. Delivery by caesarean section is planned at term if the placenta praevia persists. However, vaginal delivery is possible if the placenta ‘migrates’ to its normal location before term.
3. Mild bleeding – If bleeding is minimal and the baby is immature (less than 36 weeks), you may need to be observed on admission in the hospital for few days / weeks (depending on the gestational age) before delivery, in order to allow the baby mature better.
4. Severe bleeding – If bleeding is severe at presentation or becomes severe on admission, immediate delivery by caesarean section is recommended.
5. Mother and baby’s health status – If delaying delivery will put the life of the mother or baby in danger, delivery (caesarean section) is recommended.

What preparation is required while on admission?

After the first bleeding episode, you will be admitted in the hospital till delivery, if the baby is not yet mature for delivery. The hospital must be able to carry out caesarean section at short notice. Intravenous line will be put in place and blood will be made available in case uncontrollable bleeding starts suddenly. You may be given medications to hasten the baby’s lung maturity in anticipation of premature delivery.

What are the complications of placenta praevia?

Possible complications include:

1. Bleeding: Placenta praevia can cause severe bleeding during pregnancy, delivery and post-delivery
2. Shortage of blood (shock; anaemia): Excess bleeding may result in shock and anaemia.
3. Premature delivery: Placenta praevia may lead to early delivery of baby before term. This may lead to complications in such babies like low birth weight and difficulty in breathing (due to poorly developed lungs)
4. Abnormally adherent placenta: Placenta implanting at the lower segment of the uterus may infiltrate the muscles of the uterus and be difficult to separate after delivery of the baby. This may result in uncontrollable bleeding that may lead to removing the uterus

How can placenta praevia be prevented?

Placenta praevia is difficult to prevent because the cause of majority of cases is unknown. However, certain known risk factors can be modified. These include: 

1. Cessation of smoking or cocaine
2. Adequate control of diabetes in pregnancy
3. Correction of anaemia in pregnancy
4. Reduction of the number of embryos transferred during assisted reproductive technology to reduce the number of multiple (twin, triplet) pregnancies