Placenta Previa: Causes, Risk, & Treatment

The placenta is a pancake-shaped organ found in pregnant women. It is responsible for providing nutrients, oxygen and thermo-regulation to the foetus while protecting it against internal infections. The baby is connected to it via the umbilical cord from where it receives the nutrients needed to develop. Placenta connects the developing foetus to the uterine wall of the mother. Attached to the walls of the uterus, the foetus’s umbilical cord develops from it. 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 is responsible for removing waste from the foetus’s blood
• It attaches the foetus to the walls of the uterus and keeps the baby in a proper position providing security

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. Playing an important role in the development of the baby, a healthy placenta goes a long way in ensuring a safe pregnancy.

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’ or low-lying placenta. This 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 causing severe bleeding to the mother which will affect the child too. The child may be born with defects or premature or underweight.

Does Placenta previa Cause Pain?

Placenta previa does not normally cause any 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. According to research, placenta previa occurs in 1 out of 200 pregnant mothers every year.

How Does Placenta Previa Affect the 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 separates from the uterus, endangering both the baby and the mother.

Vaginal Bleeding With Previa

Vaginal bleeding is the most serious risk 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.

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 it moves upwards and settles in the upper half of the uterus. However, when this movement of placenta does not occur properly by the third trimester, it results in the development of placenta previa.

Placenta previa is classified on the basis of the area of the cervix that the placenta covers. Based on the position of the placenta in the uterus, it may be categorised further. Posterior placenta previa is when the placenta is positioned towards the back of the uterus, while anterior placenta previa is when the placenta is positioned towards the front of the uterus, somewhere near the belly button.

What are the Different Types of Placenta Previa?

The type and severity of placenta Previa condition are decided by the coverage of the cervical area of the uterus by 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

Here, a part of the opening of the cervix is covered by the placenta. In this, the placement of placenta is on the right border of the cervix. There is a possibility of vaginal delivery if the mother has partial placenta previa.

Total Placenta Previa

In this condition, the whole cervix opening is covered by the placenta. The mother 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.
• The size of the uterus seems larger than it should be as per gestational age
• Cramping accompanied by sharp pains

If any of these symptoms are diagnosed, one must consult a doctor and start taking the precautionary measures prescribed.

Causes of Low Placenta in Pregnant Women

It is yet not established why placenta previa occurs, but there seems to be some correlation between its occurrence and past problems or habits of a patient. Here are a few of the possible causes of placenta previa:

• The age factor: Placenta previa is more common among women who are 35 years or older.
• Pregnancy history/ current condition: 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 facing placenta previa.
• Shape of the uterus: If a woman has an abnormally shaped uterus, she is at risk of having placenta previa.
• Smoking/drugs consumption: Some experts believe that women who smoke or are addicted to drugs are also at a much greater risk of having this condition.

• The habitat of the mother: Some experts believe that women who live at a higher altitude have more chances of the occurrence of placental previa.
• Past miscarriages/abortions: Women who have gone through an abortion or miscarriage have a higher risk of suffering from placenta previa.
• Baby’s position: Besides the factors which are mentioned above, the position of the baby is a significant factor which may result in placenta previa. If the baby is in the buttocks first(Breech) or is lying horizontally in the womb(Transverse) position, the chances of placenta previa increase manifold.
• 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 have caused placenta previa.
• Size of the placenta: An inherently large placenta can cause it as well.

Treatment for Low Lying Placenta in Pregnancy

The treatment plan a doctor recommends differs from patient to patient depending on the health of the mother and the child. If placenta previa is diagnosed in the early phase of pregnancy, 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 a 36-week 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 recognising the antigens. It is given via an intramuscular injection. In most cases, pregnant women develop 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 baby’s lungs, doctors sometimes provide steroid injections. C- section is recommended and performed as the last resort when the heavy bleeding cannot be managed by doctors. A doctor may also perform an Amniocentesis test to check the growth and health of the foetus for a premature delivery.

Medication – There is no specific medication offered as a cure for placenta previa. Doctors recommend taking iron supplements, as the mother 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- Delay preterm labour.
• Corticosteroids – In case of mild bleeding.
• Dexamethasone- Develops the lung of the foetus.
• Betamethasone- Aids in the lung development of the foetus.
• Terbutaline-Used to relax the uterine contractions.

Medical Intervention: Different kinds of medical interventions may be used to ensure the safety of the mother and the child when placenta previa has been diagnosed. Some of them are listed below:

• Intravenous Therapy: This is prescribed by 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 mother and the child. An external monitoring device is used to observe and monitor the foetal heartbeat and contraction of the uterus.
• Surgery: Surgical management is availed by doctors only if there is a threat to the life of the mother and the baby. If the placenta has covered more than 30% of cervix opening, a foetus can’t pass through it, and hence C-section is performed by doctors

Diagnosis and Management of Placenta Previa

A Placenta Previa ultrasound is the most common and the most accurate method to diagnose the condition. The diagnosis may need the following steps-

1. Transvaginal ultrasound– helps measure the distance between the placenta and the opening of the cervix. Hence it can accurately provide inputs about the presence or absence of this condition.

2. Transabdominal ultrasound– This is done to check the pelvic organs and to investigate the growth of the foetus.

3. MRI (Magnetic resonance imaging)– 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 the progress of time, but in cases 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 for worry. It is quite natural in the initial stages, but as the pregnancy progresses, the placenta should move upwards with the expansion of the uterus. If the placenta is still blocking the cervical region after 20 weeks, there a likelihood of placenta previa existing. By 20 weeks or 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:

Placenta Previa Effects on the Baby and the Mother

Effects on the Mother

• Excessive loss of blood: Placenta previa may cause excessive bleeding during delivery and pose a health risk to the mother.
• Placenta accreta: In this condition, the placental tissues are too deeply embedded in the womb. They attach to the muscle layer and do not separate from the wall of the uterus during delivery. This may lead to bleeding which may endanger the life of the mother. Placenta accreta normally requires a hysterectomy during a c-section delivery.

Placenta Previa may affect the baby in the following cases:

• 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 child.
• Premature Birth: If vaginal bleeding is excessive, the doctors may decide to deliver the baby pre-term. If the baby is born very early, he/she may face long-term health and developmental issues.

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 location and position of the foetus in the uterus, decides whether it shall be a normal delivery or a C-section delivery. If the placental previa is developed in the later phase of the pregnancy, there are higher chances of C-section delivery.

While placenta previa may be a worrying condition, it is by no means one which is sure to put a pregnancy at risk. Constant monitoring, preventive medication, rest, and post-operative care ensure that most placenta previa deliveries are safe ones. While almost all of them are C-sections, it is not impossible to have a vaginal delivery in cases of marginal placenta previa. Do remember that a low-lying placenta in early pregnancy is common, and is most likely to move up on its own.