What Complications Can Affect the Placenta?

The placenta is a vital part of growing a baby. Mothers-to-be grow this brand new temporary organ alongside their baby, and it serves as the baby’s lifeline during pregnancy. There are, however, some pregnancy complications that can affect the placenta at different weeks of pregnancy. We’ve outlined some of the most common placental complications below, along with symptoms, risk factors, and what they may mean for both mother and baby.

[Updated January 2026]

The placenta is attached to the wall of the uterus and connects to the baby via the umbilical cord. This connection allows oxygen, nutrients, and antibodies to pass from mother to baby, while waste products are removed from the baby’s bloodstream. The placenta also produces hormones essential for maintaining pregnancy and supporting the baby’s development.

Throughout pregnancy, this remarkable organ adapts and grows to meet the changing needs of the baby, regulating blood flow, supporting the formation of vital blood vessels, and ensuring the baby receives enough oxygen and nutrients at each stage of pregnancy.

Read more about the different stages of pregnancy in our pregnancy week by week guide here.

Placental Location: What’s Normal and What’s Not

You might be told that you have an anterior or posterior placenta during a routine pregnancy scan. Neither of these positions are anything to worry about and simply describe where the placenta is attached to inform your healthcare provider, either the front or back wall of the uterus.

This positioning may affect how strongly you feel your baby’s movements, especially earlier in pregnancy, but it should not impact your baby’s health or your delivery. You’ll often hear people mention that they didn’t feel their baby kick for the first time until later in their pregnancy than a friend due to their anterior placenta.

A low-lying placenta, however, is different. This is where the placenta implants closer to the cervix, near the birth canal, and may require closer monitoring by your healthcare provider as pregnancy progresses.

There are some complications like the above that can affect the placenta during pregnancy that might impact its function or the maternal or infant’s health. These can lead to challenges during pregnancy or delivery. We’ve outlined some of the most common conditions below.

Placenta Previa (Placenta Praevia)

Placenta previa (also known as placenta praevia) occurs when the placenta partially or completely covers the cervix, the opening to the birth canal where the baby exits the body at birth.

Placenta previa is usually identified during the second trimester anatomy scan. In many cases, the placenta moves upwards as the uterus expands, resolving naturally by the third trimester.

Symptoms

Placenta previa often causes no symptoms. When symptoms do occur, they may include:

• Vaginal bleeding, often painless
• Bleeding that occurs suddenly in late pregnancy
• Bleeding that may be heavy or recurrent

Any vaginal bleeding during pregnancy should be assessed by a health care provider, as it can be a sign of a problem requiring immediate attention.

Risk Factors

Certain factors can place a pregnant person at higher risk of placenta previa, including:

• Previous pregnancies
• Previous C section
• Scar tissue on the uterine wall
• Carrying multiple babies
• A history of uterine surgery
• High-risk pregnancy classification

Why Placenta Previa Matters

If placenta previa persists into late pregnancy, it can cause heavy bleeding or life-threatening bleeding during labour. In these cases, a planned caesarean section (C section) is usually recommended, as vaginal birth could lead to uncontrolled bleeding.

Placenta previa is a common placental complication, but with careful monitoring and a clear treatment plan, the vast majority pregnancies with placenta previa result in healthy live births.

Placental Abruption 

Placental abruption, also called abruptio placentae, is a serious condition in which the placenta separates prematurely from the uterine wall.

When the placenta separates, blood flow to the baby is disrupted. This can reduce oxygen delivery, depriving the baby of oxygen and nutrients, and may result in a medical emergency.

Symptoms of Placental Abruption

Symptoms of placental abruption may include:

• Abdominal pain
• Vaginal bleeding (which may be light or severe)
• Uterine tenderness
• Frequent contractions
• Much pressure in the abdomen

In severe placental abruption, bleeding may be concealed behind the placenta, meaning vaginal bleeding may be minimal even though the condition is serious.

Risk Factors for Placental Abruption

Several factors can increase the risk of placental abruption, including:

• High blood pressure
• Gestational diabetes or cases of uncontrolled diabetes
• Cocaine use
• Smoking
• Previous pregnancies affected by placental abruption
• A history of placental abruption
• Trauma to the abdomen

Potential Outcomes

Placental abruption can lead to:

• Preterm labor
• Premature birth (you can find out more about premature births here)
• Pregnancy loss in severe cases
• Need for emergency delivery
• Admission to a neonatal intensive care unit (NICU)

Prompt assessment, blood tests, a physical exam, and imaging are essential when symptoms like these appear.

Retained Placenta

After childbirth, the placenta normally separates from the uterine wall and is delivered during the third stage of labour, usually within 30 minutes.

A retained placenta occurs when all or part of the placenta remains inside the uterus. 

Risks of Retained Placenta

Retained placenta can lead to:

• Severe bleeding
• Infection
• Postpartum haemorrhage
• Need for surgical removal
• Blood transfusion in severe cases

Prompt treatment by a healthcare provider reduces the risk of complications. Medical intervention, sometimes including surgery, is often needed to remove the retained tissue.

Placental Insufficiency (Placental Dysfunction)

Placental insufficiency occurs when the placenta does not function effectively, limiting the transfer of oxygen and nutrients to the baby.

This condition can develop gradually and may be linked to:

• Reduced blood flow through the placenta
• Damage to placental blood vessels
• Underlying medical conditions

Impact on Baby

Placental insufficiency may lead to:

• Intrauterine growth restriction (IUGR)
• Growth problems where the baby is smaller than the expected gestational age
• Little amniotic fluid or little fluid overall
• Increased risk of preterm birth

Close monitoring, growth scans, and careful planning around delivery are often required to protect baby’s health.

Placenta Accreta

Placenta accreta is a condition where the placenta attaches too deeply into the uterine lining, making it difficult to detach after delivery.

This is considered a high-risk placental complication and is more likely in women with:

• Previous caesarean section
• Scar tissue in the uterus
• Placenta previa combined with uterine scarring

Why Placenta Accreta Is Serious

In severe cases, placenta accreta can cause:

• Life-threatening bleeding
• Need for blood transfusion
• Emergency surgery
• Hysterectomy in rare cases

Placenta accreta is often diagnosed before birth and managed by specialist medical professionals in a hospital setting.

Ectopic Pregnancies and Placental Development

While ectopic pregnancies are not placental complications themselves, they are important to mention when discussing placental development.

An ectopic pregnancy occurs when a fertilised egg implants outside the uterus, most commonly in the fallopian tube. This prevents normal placental development and is a medical emergency which requires treatment.

Risk Factors for Ectopic Pregnancy

• Previous ectopic pregnancies
• Tubal sterilization procedures
• Pelvic infections
• Scar tissue in the fallopian tubes
• Increased risk after fertility treatments

Treatment of an ectopic pregnancy may involve medication or surgery and does not result in a viable pregnancy.

Do Placental Complications Affect Cord Blood Collection?

In some cases, placental complications can affect the ability to collect cord blood. Factors such as early delivery, abnormal placental attachment, or reduced blood volume in the placenta may result in a small amount of cord blood being available.

At Smart Cells, our minimum cord blood collection volume is 10ml to ensure sufficient stem cells for processing and storage.

Fortunately, the inability to collect enough cord blood is relatively rare. In 2023, only 5.8% of our cord blood collections had volumes below 10ml, whether due to placental complications or other factors such as umbilical cord length.

What Happens to the Placenta After Birth?

After your baby is born, the placenta is delivered during the final stage of labour. This usually occurs within an hour and is monitored closely by your healthcare provider to ensure the placenta separates fully and safely.

Some parents choose to preserve the placenta for personal, cultural, or medical reasons, including placental tissue banking.

When the placenta is delivered with the cord still attached to the baby and left unclamped and uncut, this is called a lotus birth.

In most cases though, the placenta along with the cord blood and tissue is discarded and thrown away as medical waste, meaning that the stem cells contained within it can’t be saved or used for potential future treatments.

Delayed cord clamping is now widely recommended and is fully compatible with cord blood collection.