Placenta Previa – Causes, Risks & Treatment

The placenta is a pancake-shaped organ that grows inside the lining of a woman’s uterus when she is pregnant. It carries oxygen and nutrients to the foetus while protecting it against internal infections. The placenta connects to the baby through the umbilical cord. Placenta connects the developing foetus to the uterine wall of the mother.

If the pregnancy progresses normally, the placenta gets attached to the top right or top left of the uterus. It moves up or to the side as the womb stretches during pregnancy. A normal placenta looks like an oval disk with a cord attached to its centre and a healthy placenta goes a long way in ensuring a safe pregnancy.

Here are a few important functions that the placenta performs.

• It helps hormone generation to further the growth of the foetus in the uterus.
• It helps removes waste from the foetus’s blood.
• It attaches the foetus to the walls of the uterus and keeps the baby in a proper position.

What Is Placenta Previa?

During the course of pregnancy, if the placenta develops in a way that it covers the cervix completely or partially, the condition is termed as ‘Placenta Previa’. This condition poses a risk to the baby and the mother during labour and delivery, as it may get damaged when the cervix opens. The placenta may detach itself too early from the uterus and lead to severe bleeding. And the child may be born prematurely and underweight and with birth defects.

Does Placenta Previa Cause Pain?

Placenta previa does not normally cause pain during pregnancy. However, if any discomfort is experienced, it is advisable to speak to a doctor about it.

Is Placenta Previa Common?

Placenta previa is a rare medical condition that develops in pregnant women. This condition is known to occur in 1 out of 200 pregnant women every year.

How Does Placenta Previa Affect a Pregnancy?

Since the cervix is covered in this condition, placenta previa comes in the way of the passage of the baby during delivery. Placenta previa thus poses a challenge at the time of labour and delivery. It may also cause a rupture in the blood vessels in the pelvic region as the cervix expands, and in certain cases, lead to placental abruption where the placenta may separate from the uterus, endangering both the baby and the mother.

Is Vaginal Bleeding a Symptom of Placenta Previa?

Yes, vaginal bleeding is a common symptom of placenta previa. In fact, it is the most serious risk that placenta previa poses. This is most likely to occur in the third trimester when the lower lining of the uterus thins to prepare for delivery. This may cause bleeding in the placenta covering the cervix. However, a pregnant woman can also experience painless vaginal bleeding as early as 20 weeks of pregnancy, especially in the case of a complete placenta previa.

What Does It Mean to Have a Low-lying Placenta?

A low-lying placenta is attached to the lower region of the uterus in close proximity to the cervix, as against its usual position of upper or side upper regions in a normal pregnancy. The placenta is attached to the lower part of the uterus in the early stages of pregnancy and with time moves upwards and settles in the upper half of the uterus. However, when this movement of the placenta does not occur properly by the third trimester, it results in the development of placenta previa.

What Are the Different Types of Placenta Previa?

The type and severity of the placenta previa condition are decided by the coverage of the cervical area of the uterus by the placenta which may be partial or full. Following are the types of placenta previa:

Marginal Placenta Previa

In this type of placenta previa, the edge of the placenta is implanted very close to the cervix, but the cervix is not covered completely.

Partial Placenta Previa

Partial placenta previa is when a part of the opening of the cervix is covered by the placenta. In this, the placement of the placenta is on the right border of the cervix. There is a slight possibility of a vaginal delivery if the pregnant woman has partial placenta previa.

Total Placenta Previa

In this condition, the opening of the cervix is entirely covered by the placenta. A pregnant woman in this case usually requires a caesarean delivery. Also known as central placenta previa, this is the position which causes maximum complications during delivery.

Symptoms of Placenta Previa

There are different signs and symptoms which can predict the possibility of placenta previa. Here are a few to watch out for.

• Painless bleeding from the second trimester. This bleeding may occur in phases of two to three weeks, or it may be more frequent and without any specific reason.
• The bleeding may also happen along with premature contraction if the position of the foetus is transverse or breech.
• Cramping accompanied by sharp pain.

If any of these symptoms are experienced, you must consult a doctor and start taking the precautionary measures prescribed by her.

Causes of Placenta Previa During Pregnancy

It is yet not established why placenta previa occurs, but there seems to be some correlation between its occurrence and problems before pregnancy or lifestyle of the woman. The occurrence of this condition depends on the following factors.

• Age: Placenta previa is more common among women who are 35 years or older.
• Pregnancy History: Women with many previous pregnancies or those who have multiple pregnancies like twins or triplets face this condition more than other women.
• Surgical History: A woman with a history of uterus surgery, which may or may not include an incision, is at a higher risk of this complication.
• The Shape of the Uterus: If a woman has an abnormally shaped uterus, she is at the risk of having placenta previa.
• Smoking/Taking Drugs: Some experts believe that women who smoke or are addicted to drugs are also at a much greater risk of having this condition.

• Past Miscarriages/Abortions: Women who have had an abortion or a miscarriage have a higher risk of suffering from placenta previa.
• Demographics: The chances of placenta previa also vary demographically. For e.g., Asian women have a higher likelihood of having placenta previa.
• Dilation and Curettage (D&C) Surgeries: Past record of undergoing these surgeries are also known to cause placenta previa.
• Size of the Placenta: An inherently large placenta can even be one of the causes of the placenta previa.

Treatment for Low-lying Placenta in Pregnancy

The treatment suggested for this condition will differ for pregnant women. The treatment offered will also depend on the health of the mother and the baby. If placenta previa is diagnosed in the early phase of pregnancy and is partial placenta previa, it may even resolve on its own.

The treatment protocol is decided on the basis of the amount of bleeding. The doctor restricts activities and advises bed rest in case of light bleeding. In certain cases of heavy bleeding, blood transfusion is suggested as an important part of the treatment procedure. Often medicines are given to the mother to prevent early labour and premature delivery, and to help complete at least 36-weeks gestation.

For a patient with Rh-negative blood type, doctors provide RhoGAM as a special medicine. It is given both during and after pregnancy, and it works by blocking the immune system from recognizing the antigens. It is given via an intramuscular injection. In most cases, pregnant women require an anti-D during pregnancy only after 28 weeks of gestation. which is why Rhogam is majorly given after 28 weeks of pregnancy.

For better development of the baby’s lungs, doctors sometimes provide steroid injections. A C-section is recommended and performed as the last resort when the heavy bleeding cannot be managed by doctors.

Medication – There is no specific medication offered as a cure for placenta previa. Doctors recommend iron supplements, as the pregnant woman may become anaemic due to heavy blood loss. Some drugs and supplements that may be prescribed by the doctor are mentioned below –

• Tocolytics- To avoid premature delivery.
• Magnesium Sulphate – To delay preterm labour.
• Dexamethasone – For the healthy development of the lungs of the baby.
• Betamethasone – To aid the development of the lungs of the foetus.
• Terbutaline- To relax the uterine contractions.

Medical Intervention – If placenta previa has been diagnosed and the condition is severe, then medical intervention is necessary to ensure the safety of the mother and the child. The following is suggested.

• Intravenous Therapy: This is prescribed by the doctors when there is a requirement of blood replacement that was lost during the bleeding.
• Regular Monitoring: Vaginal examinations are avoided as they may cause haemorrhage which could be life-threatening for both the mother and the child. An external monitoring device would be used to observe and monitor the foetal heartbeat and contraction of the uterus.
• Surgery: The doctor will recommend surgery if there is a threat to the life of the mother and the baby. If the placenta covers more than 30% of the opening of the cervix, the foetus can’t pass through it, hence a C-section will be performed.

Diagnosis of Placenta Previa

An ultrasound is the most accurate method for diagnosing this condition. The following scans are conducted to detect placenta previa – 

1. Transabdominal Ultrasound – A transabdominal scan is done to check the pelvic organs and to check for the growth of the foetus.

2. Magnetic Resonance Imaging (MRI) – This determines the location of the placenta clearly.

Placenta previa can be diagnosed from the second trimester of pregnancy during a routine ultrasound examination. In cases of marginal implantation of the placenta or partial placenta previa, the situation may improve with time, but in the case of total placenta previa, it is unlikely to resolve on its own.

While routine early ultrasound scans may show that the placenta is lying low and is quite near the cervix, this is not a cause of worry. It is quite common in the initial stages of pregnancy, but with time, the placenta should move upwards as the uterus expands. If the placenta is still completely blocking the cervical region after 20 weeks, there a likelihood of placenta previa existing even at term. By  the third trimester, the placenta should be at a sufficient height so as to not block the cervix.

What If Placenta Previa Is Present During Labour and Delivery?

The presence of placenta previa during labour and delivery can pose a threat to both the baby and the mother. Some complications which may arise are stated below.

Effects on the Mother

• Excessive loss of blood: Placenta previa may cause excessive bleeding during delivery and pose a risk for the health of the mother.
• Uterine atony: Atony of the uterus may result in heavy blood loss and may also lead to unplanned hysterectomy.

Effects on the Baby

• Placental abruption: This is a condition where the placenta separates from the uterus, disrupting the supply of blood and nutrients to the baby, and may endanger the life of the unborn baby.
• Premature birth: If vaginal bleeding is excessive, the doctors may decide to deliver the baby preterm. And if the baby is born premature, he may face health and developmental issues in the long run.

Other Common Placental Problems

While a low lying placenta is the most discussed placental problem as it is common in early pregnancy, there are other conditions which may affect placental health. Some of these are:

• Placental insufficiency: In this condition, the placenta is unable to provide sufficient nutrition to the growing foetus. This can lead to low birth-weight.
• Infarcts in the placenta: Infarcts are areas of dead tissue in the placenta which cause reduced blood flow. They may be caused by pregnancy-induced hypertension. These are normally harmless, but in extreme cases, they may risk the baby’s health or survival.
• Placental abruption: In this condition, the placenta partially or completely breaks away from the uterus, reducing or stopping the blood supply to the foetus. This rare condition can be fatal.
• Placenta accreta: In this condition, the placenta is too deeply embedded in the wall of the uterus. This may lead to excessive bleeding after delivery. Surgery may be required to remove the tissue from the uterus post-delivery in such cases.

Delivery With Low-Lying Placenta

The health of the foetus and the mother, as well as the location and position of the foetus in the uterus, decides whether it shall be a normal delivery or a C-section delivery. If this condition develops in the later phase of the pregnancy, there will be higher chances of C-section delivery.

Although placenta previa poses risk to the health of the mother and baby, one should not lose hope. Constant monitoring, preventive measures, ample rest, and post-operative care ensure that both the mother and the child stay safe. It is not always impossible to have a vaginal delivery in cases of marginal placenta previa, but a low-lying placenta in early pregnancy is common, and is most likely to move up on its own. If you have placenta previa, go for regular checkups and do as your doctor suggests. Your doctor will guide you the best. Have a safe pregnancy!