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Placenta Previa

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Facts

The placenta is a bed of cells formed inside the uterus (womb) during pregnancy. The purpose of the placenta is to carry nourishment and oxygen from the parent to the fetus and to carry waste products and carbon dioxide from the fetus to the parent through the umbilical cord.

The placenta is usually formed along the upper part of the uterus, allowing enough space for the fetus to grow. In placenta previa, the placenta starts forming very low in the uterus or even over the cervix (the opening of the uterus that leads to the vagina). This obstruction impairs normal vaginal delivery of the baby at birth.

There are 3 types of placenta previa:

  • complete placenta previa: The internal cervical opening is completely covered by the placenta.
  • partial placenta previa: The internal cervical opening is partially covered by the placenta.
  • marginal placenta previa: The placenta is at the edge of the internal cervical opening.

A “low-lying” placenta does not cover or touch the cervix, but is within 2 centimetres of the opening. Placenta previa is estimated to occur in 1 in 250 pregnancies.

Causes

The causes and risk factors for placenta previa are:

  • The fertilized egg implanted very low in the uterus, causing the placenta to form close to or over the cervical opening.
  • The lining of the uterus (endometrium) has abnormalities such as fibroids or scarring (from previous previa, incisions, caesarean sections or abortions).
  • The placenta formed abnormally.
  • The pregnancy is multiple (i.e., twins or triplets). The chances of developing placenta previa are doubled for these pregnancies.
  • The birth parent may have had several previous pregnancies. The chances of developing placenta previa are increased to 1 in 20 for people who have had 6 or more pregnancies.
  • The birth parent smokes or uses cocaine. Smoking and cocaine use can increase the risk of this condition.
  • The birth parent is older. The risk of developing placenta previa is 3 times as high in people over 30 years of age as in people under 20 years of age.
  • The pregnancy has been conceived with the help of assisted reproductive technology, such as in-vitro fertilization.

Treatment and Prevention

Placenta previa is a condition that cannot be prevented. However, if you are at high risk, talk about this with your health care provider to avoid complications.

The treatment for placenta previa is usually aimed at minimizing symptoms and ensuring the pregnancy completes 36 weeks. The goal of this treatment is safe delivery of the fetus as close to term as possible by caesarean section. The treatment will therefore depend on answers to the following questions:

  • What is the extent or amount of abnormal bleeding?
  • How much of the placenta is covering the cervix?
  • What is the position of the fetus in the uterus?
  • Is the fetus developed enough to survive outside the uterus?
  • How many births has the parent previously had?
  • Has labour commenced?

Once placenta previa has been diagnosed, further bleeding and complications may be avoided by ensuring the parent has complete bed rest, sometimes in the hospital. Also, pelvic examinations or any sexual activity that may lead to irritation of the cervix or the uterine walls should be avoided.

Once the pregnancy comes to term, or if the bleeding is excessive, the baby will be delivered by caesarean section, especially in cases of complete placenta previa. Vaginal delivery for people with placenta previa might result in placental tear and hemorrhage, putting the parent and the baby at risk. Vaginal delivery may be possible for a person with a low-lying placenta.

With early and more accurate diagnosis of placenta previa, this condition is no longer as big a threat to the parent and the baby as it historically was. The biggest danger remains premature delivery of the baby because of the heavy bleeding. Corticosteroids may be given to help the baby’s lung development if premature delivery cannot be avoided.

All material copyright MediResource Inc. 1996 – 2025. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source: www.medbroadcast.com/condition/getcondition/Placenta-Previa

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