First episode of bleeding occurs:

After 36^th week: 60%

32-36^th week: 30%

Before 32^nd week: 10%

Bleeding is painless and recurrent.

Presenting part is usually high and not central to the pelvic brim.

Diagnosis is by ultrasound showing that the placenta is praevia.

Placenta praevia occurs in the second half of pregnancy when the placenta lies too low in the womb (uterus).

A low-lying placenta is often diagnosed during an early ultrasound scan. Only around one in ten women (or 10%) who have a low-lying placenta in early pregnancy will go on to have placenta praevia.

Placenta praevia can be very serious as there is a risk of severe bleeding and this may threaten the health and life of the mother and baby.

Maternal deaths from placenta praevia are fortunately extremely rare. Each year in the UK, there are 600,000 deliveries; about three women die as a result of placenta praevia.

If you have a major degree of placenta praevia you will need a caesarean section.

The placenta develops along with the baby in the womb during pregnancy. It links the baby with the mother's blood system and provides the baby with its source of oxygen and nourishment. The placenta is delivered after the baby, and is also called the afterbirth.

In some women the placenta attaches too low in the womb and covers a part or all of the entrance to the womb (cervix). This attachment often shows up in ultrasound scans at around 20 weeks, when it is called a low-lying placenta. In most cases, the placenta is subsequently appears to move upwards, as the womb stretches around the growing baby, and so it does not cause a problem. For some women, however, the placenta continues to lie in the lower part of the womb into the last months of pregnancy. This condition is known as placenta praevia. If the placenta covers the entrance to the womb (cervix) entirely, this is known as major placenta praevia.

Rarely, placenta praevia may be complicated by a problem known as placenta accreta. This is when the placenta is attached to the womb abnormally, making separation at the time of birth difficult. Placenta accreta is more commonly found in women with placenta praevia who have previously had a caesarean section.

If you have placenta praevia you may experience vaginal bleeding late during your pregnancy, although this could be due to some other cause. Bleeding from placenta praevia can occasionally be very severe, and so put the life of the mother and baby in danger. Because bleeding can be treated, however, deaths from placenta praevia are rare. In the UK, about three women out of every 600,000 who give birth each year die as a result of placenta praevia.

If the placenta stays low in the womb, the baby may still be lying bottom first (known as the breech position) or lying across the womb (known as transverse) around the time of birth.

Women with placenta praevia usually need a caesarean section and may need a blood transfusion. Rarely, the bleeding is so severe that the only way it can be controlled is by removing the womb (hysterectomy).

If there is a lot of bleeding before the baby is due to be born, the doctors may have to deliver your baby prematurely by caesarean section. The earlier the baby is born before the due date, the higher the risk of health problems. The risk is greatest if the baby is born very early, that is, before 31 completed weeks of pregnancy. Premature babies may have problems with normal activities such as feeding and breathing, and they are at greater risk of having health problems such as infection and jaundice. Because of this, early delivery by caesarean section is only considered if the bleeding is severe enough to cause risk to the mother or baby.

Diagnosis of placenta praevia.

A low-lying placenta is often suspected during a 20-week ultrasound scan. The majority of women who have a low-lying placenta in early pregnancy will not, however, go on to have placenta praevia; about one in ten of these women (or 10%) will go on to have placenta praevia. Occasionally placenta praevia may be picked up later in pregnancy, if the baby is found to be lying in an awkward position or if you have been bleeding. For most women a diagnosis of placenta praevia is made in the second half of pregnancy. The best way to confirm whether or not you have placenta praevia is with a transvaginal ultrasound scan.

If your doctor thinks you may have placenta praevia (for instance, if you have vaginal bleeding) you may be offered additional ultrasound scans to investigate and monitor the pregnancy.

Management of placenta praevia.

You may have been advised to avoid having sexual intercourse during pregnancy, particularly if you have been bleeding.

You may be offered an examination with a speculum (a plastic or metal instrument used to separate the walls of the vagina) to see how much and where your bleeding is coming from. This is an entirely safe examination.

If you have placenta praevia you should eat a healthy diet rich in iron to reduce the risk of anaemia.

Unless there is severe bleeding or another indication, delivery by caesarean section should be performed after 38 weeks.

You have the right to be fully informed about your health care and to share in making decisions about it. Your healthcare team should respect and take account of your wishes. 

One extra scan may be all that is needed to monitor the position of the placenta. If your placenta is no longer low-lying, you will have normal antenatal care.

If your placenta remains low-lying in the second half of pregnancy (after 20 weeks), you will have at least one more transvaginal ultrasound scan to check whether the position of the placenta has altered with the development and stretching of the womb. Additional extra care will be given based on your individual circumstances.

If you have major placenta praevia or placenta accreta is suspected, you may be offered admission to hospital after 34 weeks of pregnancy. Even if you have had no symptoms before, there is a small risk that you could bleed suddenly and severely, which may mean that you need an urgent caesarean section.

If you have placenta praevia and have no bleeding, then you may be able to have care at home. However, you should be able to get to hospital quickly and easily at any time. You should call for an ambulance, should this need arise.

After you have been told that you have placenta praevia, you and your partner should have the opportunity to discuss the options for delivery with your doctor.

In a few instances, a blood transfusion is essential to save the life of the mother and baby. If you feel that you could never accept a blood transfusion, then you should explain this to your obstetrician and midwife as early as possible. You can then discuss any objections or particular questions that you may have.

Delivery in the presence of placenta praevia.

Your healthcare team will recommend the best way for you to give birth based on your own individual circumstances.

If, on your scan at 32 to 36 weeks, your placenta is less than 2 cm from the entrance to the womb (cervix), you will almost certainly need a caesarean section. If this is the case, you should be delivered by the most experienced obstetrician and anaesthetist on duty. A consultant obstetrician and anaesthetist should be present within the delivery suite at this time. This is particularly important if you have previously had a caesarean section.

If an emergency arises, a consultant will be present.

Your anaesthetist will discuss the options for anaesthesia if you need a caesarean section. You may need to have a general anaesthetic.

If you have a caesarean section because of placenta praevia, you are more likely to need a blood transfusion. Blood supplies should be available, as necessary, for your individual circumstances.

It may be hard to be sure whether there is placenta accreta before surgery, but if this is thought to be likely your doctor may explain it to you beforehand.

Placenta praevia is a high risk complication of pregnancy with risks for mother and baby ⁰³⁰¹      With the rising incidence of caesarean section operations combined with and increasing maternal age, the numbers of cases of placenta praevia and its complications will continue to rise.

Transvaginal ultrasound is safe in the presence of placenta praevia and is more accurate than transabdominal ultrasound in locating the placenta.⁹⁹⁰¹ In cases of asymptomatic suspected minor praevia, follow-up imaging can be left until 36 weeks.In cases with asymptomatic suspected major placenta praevia, a transvaginal ultrasound scan should be performed at 32 weeks, to clarify the diagnosis and allow planning for third-trimester management and delivery.

Placental migration occurs during the second and third trimesters, owing to the developmentof the lower uterine segment, but it is less likelythere has been a previous caesarean section.⁰²⁰² Ideally, antenatal imaging by colour flow Doppler ultrasonography should be performed in women with placenta praevia who are at increased risk of placenta accreta. Where this is not possible locally, such women should be managed as if they have placenta accreta until proven otherwise.

Women with placenta praevia are at increased risk of having a morbidly adherent placenta if they have an anterior placenta praevia and have previously been delivered by caesarean section⁹⁷⁰¹ especially when there has been a short caesarean to conception interval.                              

Women with major placenta praevia who have previously bled should be admitted and managed as inpatients from 34 weeks of gestation.Those with major placenta praevia who remain asymptomatic, having never bled, require careful counselling before contemplating outpatient care. Any home-based care requires close proximity with the hospital, the constant presence of a companion and full informed consent from the woman.

In selected patients outpatient management of complete placenta previa can be cost-effective and safe.9401 If bleeding occurs hospitalization is essential. Prolonged inpatient care is associated with a risk of throboembolism. Gentle mobilitsation should be encouraged together with the use of prophylactic thromboembolic stockings. Prophylactic anticoagulation should be reserved for those at high risk of thromboembolism and, in these cases, unfractionated heparin is to be preferred over the longer-acting low-molecular-weight preparations.

The mode of delivery should be based on clinical judgement supplemented by sonographic information. A placental edge less than 2 cm from the internal os is likely to need delivery by caesarean section, especially if it is posterior or thick.

Blood should be readily available for the peripartum period. Requirements for crossmatched blood and what amount will depend on the clinical features of each individual case and the local blood bank services available. When women have atypical antibodies, direct communication with the local blood bank should enable specific plans to be made to match the individual circumstance.

There is no evidence to support the use of autologous blood transfusion for placenta praevia.

The choice of anaesthetic technique for caesarean section for placenta praevia must be made by the anaesthetist, in consultation with the obstetrician and mother, but there is increasing evidence to support the safety of regional blockade.⁰³⁰²

When there has been a previous caesarean section, consultant delivery is recommended as there is an increased risk of placenta accreta.