Having low blood platelets during pregnancy is the second most common type of blood disorder, after anaemia.

Between 5-8% of women will be diagnosed with a low blood platelet count (thrombocytopenia) during pregnancy.

It is very rare for this to be a problem during pregnancy or birth, but if you are told your platelet levels are low, it’s a good idea to be prepared for the potential effects.

What Are Platelets?

Platelets are plate-shaped cells that circulate in your blood, and help it to clot when needed.

If a blood vessel in your body is injured, it sends a signal to activate the platelets, which then travel to the damaged area. When the platelets reach the injured blood vessel, they grow tentacles to help them make contact with the damaged area. This creates a blood clot and stops excessive bleeding.

The normal level of platelets is between 150 and 400 million per millilitre of blood. If you have more than 400 million, the condition is called thrombocytosis. If you have fewer than 150 million it is known as thrombocytopenia.

Most care providers recommend women have a full blood count done at some stage during pregnancy. This is a routine test to check platelet levels.

What Causes Low Platelet Levels?

The three most common causes of low platelets in pregnancy are: immune thrombocytopenia, preeclampsia, and gestational thrombocytopenia.

Immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune condition, occurring before pregnancy, where your immune system attacks the body’s platelets. It usually develops after a viral infection contracted during childhood.

Usually ITP would be diagnosed well before you become pregnant, but sometimes it is picked up in early pregnancy blood tests. If platelet levels drop below a certain level, you will usually be treated with steroids. If you have ITP, there is also an increased chance that your baby will have low platelets.

There are several symptoms of immune thrombocytopenia:

Bruising easily, or having many bruises
A rash that appears on the lower legs; this is actually bleeding under the skin
Blood in urine or stools
Bleeding gums, or a blood nose
Cuts that take a long time to stop bleeding
Unusually heavy bleeding during periods.

Preeclampsia

This is a condition presenting with high blood pressure, and protein in the urine. Low platelets can indicate a more severe form of preeclampsia, known as HELLP syndrome, often seen in the third trimester.

HELLP syndrome is a serious condition, which usually means your baby needs to be born immediately. Your baby’s platelet levels will be normal, and a few weeks after the birth your platelets will also return to the normal range.

You should be aware of the signs and symptoms of preeclampsia if you are pregnant.

Gestational thrombocytopenia

The most common cause of low platelets during pregnancy is gestational thrombocytopenia, which occurs in about 5-8% of normal pregnancies, during the third trimester.

It is not known exactly why it occurs, but it is thought to be a result of the increased blood volume as your pregnancy progresses to full term. During the last trimester, your blood plasma will have increased by almost 50%.

As the volume of plasma increases, the platelets are effectively diluted, meaning there are fewer platelets per millilitre of blood. The blood platelets can still perform their job, and will return to normal levels after your baby is born.

Other possible causes of low platelets are:

Certain medications, such as blood thinners
Kidney infections
Excessive intake of alcohol
Certain types of cancer.

What Happens If I Have Low Platelets During Pregnancy?

If you have a very low platelet count before pregnancy, or it is picked up during an early pregnancy test, it is likely to be caused by an existing condition, or a medication you are taking.

Unfortunately there is no diagnostic test to determine what is causing low platelets, so you might need to be monitored over time so your doctor can work out whether the thrombocytopenia is benign, or a sign of underlying problems.

If low platelets are picked up later in pregnancy, your doctor will look for signs that preeclampsia, or HELLP syndrome, might be developing, and will treat you accordingly.

Gestational thrombocytopenia is unlikely to require any treatment as it doesn’t cause any problems or complications. Your doctor will probably monitor your platelet levels to see whether they continue to drop or remain steady.

What Are The Risks Of Low Platelets During Pregnancy?

If you have low platelets, the main reason for concern is the increased risk of bleeding during or after the birth of your baby. This is of particular concern if you require a c-section, as there is more blood loss with a c-section birth than during a vaginal birth.

Compared with the other organs in the body, the uterus has the largest supply of blood. During the surgery, large blood vessels are cut as the uterus wall is opened. Most healthy women can tolerate this blood loss, but if your blood is not able to clot well, due to low platelets, it increases the risk of excessive blood loss, and transfusion.

It is a good idea to be informed about all the risks of c-sections, so you can make an informed decision.

If you request, or need, an epidural, the anaesthetist will need to be very cautious about placing the epidural needle. If there is an accidental puncture in the epidural space, it can cause blood to collect in one place, and put pressure on the spine (a spinal epidural hematoma).

Although this is rare, it can lead to permanent paralysis and injury to the spine. Many anaesthetists are cautious about placing an epidural if the platelets are extremely low; the cut-off point can differ depending on the hospital and the practitioner.

If a c-section is medically unavoidable, a general anaesthetic will be used instead of a spinal epidural, to reduce the risk of puncture.

Having an epidural is not risk-free at any time, so make sure you know the risks and benefits of having an epidural during labour. If you are concerned about not having the option of an epidural, it might be a good idea to learn natural pain relief methods for labour.

Low platelets during pregnancy is a common condition, which is usually rectified after birth. However, most care providers will consider a low platelet level as a risk factor for complications, regardless of how mild the thrombocytopenia might be.

Depending on your care provider’s approach to management, this can limit your options for birth. For most women, having low platelets simply means some extra monitoring during pregnancy, to determine whether there is an underlying cause. With the right support, low platelets should not greatly affect your pregnancy or birth.