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Pregnancy Bliss | Reproductive Health Hub

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Placenta praevia

What is placenta praevia?

This basically means that the placenta is low-lying.

Normally, the placenta (afterbirth) is implanted well away from the neck of the womb. In some cases, however, the placenta is very close to and even overlying the opening of the neck of the womb (cervix). This makes it prone to bleed in the course of the pregnancy.

How serious is placenta praevia?

It really depends on the degree of how close it is to the cervical opening. When it is actually covering the cervical opening, it is very serious indeed and many obstetricians will admit such a patient to hospital at a certain stage of the pregnancy, to stay in for the remainder of the pregnancy.

This is even in the absence of any bleeding. The main reason is because bleeding in major placenta praevia can be so abrupt and heavy as to endanger the lives of both mother and fetus within minutes.

Are all patients with placenta praevia delivered by caesarean section?

The majority are. Only the ones with minor placenta praevia (and all else being well) are actually allowed to have vaginal delivery. The attending obstetrician should be able to explain why he or she is advising a particular method of delivery.

What about the timing of the delivery in cases of placenta praevia?

In the absence of bleeding, efforts will be made to allow the pregnancy to get as close to term as possible.

Of course, if it is major placenta praevia, the final weeks - which may be as many as six to ten, may have to be spent in hospital. The aim is to prevent unnecessary prematurity, whenever possible. If the mother starts bleeding and if bleeding is heavy or recurrent, then there will be no option but to deliver the baby.

Some mothers with placenta praevia have no symptoms until they suffer a heavy vaginal bleed and delivery has to be made immediately. Delivery before thirty-seven weeks of gestation will have to be carried out in almost 40 per cent of such mothers.

Does this mean prematurity is a serious problem in cases of placenta praevia?

Yes. In fact, it is the leading cause of losing a baby. In this condition, the loss of babies born before twenty-eight weeks of gestation is fairly high. Even the babies that survive suffer from significant illness because of prematurity.

Are there any other problems associated with the diagnosis of placenta praevia?

Yes. Growth restriction of the fetus in the womb is commoner among women with placenta praevia, affecting almost one in six of them, a much higher incidence than in most pregnant women.

The risk of serious malformations of the fetus are also almost doubled.

For the mother herself, there is the dramatically increased risk of caesarean delivery, serious blood loss (even after delivery), and increased susceptibility to infection in the post-delivery period.

Should a woman panic If she is told that she has a low-lying placenta at her 18 - 20 weeks ultrasound scan?

No. About 18 per cent of all pregnant women (almost one in five) have a low-lying placenta at that stage of the pregnancy.

At term, only about 2 per cent (1 in 50) have placenta praevia. For the majority, changes in the course of the pregnancy result in the placenta being in a normal location. However, if a woman said to have a low lying placenta at twenty weeks bleeds vaginally at any point, she should see her doctor promptly. She might turn out to be one of the few with whom the placental location remains low.

Follow up differs in different units. Some offer a repeat scan at around 34 weeks to ascertain placental location and possibly reassure the mother. Others do not routinely offer a repeat scan and only do so if and when there is a clinical indication. There is no evidence that one strategy is superior to the other.

Are there any known causes of placenta praevia?

No causes are known but there are certainly predisposing factors. These include:

multiple pregnancy (twins or more)

multiple previous deliveries (multiparity),

older mothers (above age thirty five)

previous caesarean section

smoking during pregnancy.

Does placenta praevia recur?

Yes, but this is not common. It recurs in about 5% of affected women.

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Early pregnancy Late pregnancy Placenta praevia Placental abruption Cervical bleeding Vasa praevia