Placenta previa

Definition of placenta previa

Placenta obstructing the birth canal.

Alternative names for Placenta Previa:

1. Placenta Previa Partialis – Partial Placenta Previa
2. Placenta Previa Centraus, – Total Placenta Previa
3. Placenta Previa Marginalis – Marginal Placenta Previa
4. Mislocation of the placenta

What is placenta previa?

• Placenta previa is a placental disorder.
• The normal position of the placenta is at the upper part of the uterus.
• Placenta previa is the condition where the placenta is implanted in the lower part of the uterus.
• A low-lying placenta early in pregnancy is quite common. As the pregnancy progresses the growing uterus pulls the placenta toward the top of the uterus, which leaves the cervix clear/open for delivery.
• In some cases the placenta does not pull upwards and remains in the lower portion of the uterus.
• The placenta is therefore obstructing the birth canal.

The cervical opening can be covered in one of three ways by the placenta:

• Marginal: The placenta is located near the edge of the cervix but does not block it.
• Partial: The placenta covers part of the cervical opening.
• Complete: The placenta completely covers the cervical opening.

What causes placenta previa?

The precise cause of placenta previa is not known. However, there are certain conditions and factors with which placenta previa can be associated:

• scarring of the uterine wall from previous pregnancies
• fibroids or other abnormalities of the uterus
• previous uterine surgeries, abortion or C-section delivery
• women older than 35 years
• smoking
• placenta previa in a previous pregnancy
• multiple pregnancies (twins, triplets)
• an abnormally developed uterus
• abnormal formation of the placenta

What are the symptoms of placenta previa?

• Painless, bright red vaginal bleeding in the third trimester (week 28-40) is the main sign of placenta previa.
• The amount of bleeding may range from light to heavy. And it may stop, but it nearly always recurs days or weeks later.
• Some women who have placenta previa experience contractions with bleeding.
• Other reasons to suspect placenta previa include:
  • premature contractions
  • breech presentation baby
  • uterus measuring larger than it should

How is placenta previa diagnosed?

Placenta previa is usually diagnosed in the following two ways:

1. At a routine antenatal visit when it is picked up on an ultrasound.
2. At an emergency visit to your doctor or clinic due to vaginal bleeding.

Your doctor should not do vaginal exams if he/she suspects that you might have placenta previa as it may trigger heavy bleeding.

Your doctor will also take two other conditions, which are related to vaginal bleeding in the third trimester, into consideration when making the diagnoses. These conditions are:

• Placenta abruptio:
  • This is also a placental disorder where the placenta separates from the uterus before the birth.
• Vasa previa:
  • Blood vessels cross the cervix and therefore obstruct the birth canal.

How is placenta previa treated?

The treatment of placenta previa depends on the following factors:

• the position of the placenta (totally/partially/marginally) covering the cervix
• the position of the baby
• the stage of pregnancy
• little, no or heavy bleeding with contractions/not
• overall health of mother and baby

Different treatments:

• If you experience heavy bleeding, you may be hospitalised until the delivery, which is usually a scheduled C-section.
• You may receive medicines to prevent premature labour and help the pregnancy continue to at least 36 weeks.
• If you need an earlier C-section, you may be given corticosteroids to speed your baby’s lung development.
• If your bleeding can’t be controlled or your baby is in distress, you may need an emergency C-section – even if the baby is premature.
• You may also need blood transfusions.
• If you have marginal placenta previa or another form of placenta previa, but little or no bleeding, your doctor may recommend bed rest at home. This means only sitting and standing when necessary. You’ll need to avoid sex and vaginal exams, which can trigger bleeding.

What is the prognosis?

• All pregnant women with placenta previa are considered to be having high-risk pregnancies.
• Most cases of placenta previa are diagnosed before they become life-threatening for both mother and baby
• A scheduled C-section is almost always performed.
• If placenta previa is not diagnosed and labour starts, the placenta tends to become detached very early, depriving the baby of its oxygen supply. The lack of oxygen may result in brain damage or other problems in the baby.
• Other risk factors of placenta previa:

• It is possible that placenta previa early in pregnancy can cause a miscarriage.
• Placenta previa can also cause placenta abruptio (m ajor bleeding (haemorrhage)).
• Premature labour and birth.
• There is also an increased risk for infection and blood clots.

When to call the doctor

You should call your doctor/emergency care if you experience any form of vaginal bleeding during any stage of your pregnancy.

How can placenta previa be prevented?

• Placenta previa cannot be prevented.
• It is a pregnancy related condition which occurs in one out of 200 pregnancies.
• The best women can do is to:
  • give their doctor a full medical history of any surgeries, pregnancies, abortion or miscarriages.
  • go or all antenatal doctor’s visits and ultrasounds.
  • consult a doctor immediately of they experience vaginal bleeding.

The information provided in this article was correct at the time of publishing. At Mediclinic we endeavour to provide our patients and readers with accurate and reliable information, which is why we continually review and update our content. However, due to the dynamic nature of clinical information and medicine, some information may from time to time become outdated prior to revision.