Immune Thrombocytopenia Purpura (ITP)

Thrombocytopenia in Pregnancy

What is thrombocytopenia?

Platelets are small disc shaped cells in the blood which help to form blood clots in response to bleeding. The number of platelets range from 130 to 400 x 10(9)/L. Thrombocytopenia means the presence of a low number of platelets. Thrombocytopenia results in a tendency to bleed (such as bruising, nose bleeds) when the platelet count falls below 50 x 10(9)/L.

What causes thrombocytopenia in pregnancy?

Thrombocytopenia as defined by a platelet count less than 150 x 10(9)/L is not uncommon in pregnancy. Thrombocytopenia occurs in approximately 8% to 10% of pregnancies.

Up to 80% of pregnant patients with thrombocytopenia will have gestational thrombocytopenia (a reduction in platelets due to pregnancy because of the increased blood volume and increased platelet clearance that occur with pregnancy). Gestational thrombocytopenia is not associated with neonatal thrombocytopenia (does not cause thrombocytopenia in the newborn) or maternal morbidity (complications). Gestational thrombocytopenia usually occurs in the mid to late second or third trimester, and the platelet count will not usually fall below 70 to 80 x 10(9)/L. Occasionally the platelet count may fall below this number.

The hypertensive syndromes of pregnancy are the second most common cause of thrombocytopenia in pregnancy (for example, preeclampsia) and account for approximately 15% of thrombocytopenia in pregnancy.

Thrombocytopenia from immune related causes is uncommon in pregnancy. Three to 4% of patients who experience thrombocytopenia in pregnancy have immune thrombocytopenia, also referred to as ITP.

Thrombocytopenia in pregnancy can also be related to other rarer diseases.

What is Immune Thrombocytopenia (ITP)?

The role of the immune system is to protect against pathogens(disease-causing particles or organisms). Immune related diseases are caused by the reaction of the immune system to patients’ own cells and tissue. Immune thrombocytopenia results from an immune reaction that destroys platelets, causing thrombocytopenia. Immune thrombocytopenia may occur with other immune diseases such as Systemic Lupus Erythematosus or in the absence of other immune disease and is referred to as Immune Thrombocytopenia (ITP).

How is ITP diagnosed?

ITP is diagnosed when thrombocytopenia is found on a blood test. It is diagnosed similarly in pregnant and non-pregnant patients. A specific test is not available to diagnose ITP. All other causes of thrombocytopenia are excluded before a diagnosis of ITP can be made. It may be difficult to differentiate between ITP and gestational thrombocytopenia if thrombocytopenia only occurs in pregnancy.

How does ITP affect a pregnancy?

Pregnancy does not appear to aggravate ITP in the majority of women. Approximately 20% to 30% of pregnant patients will require treatment for ITP during pregnancy. Treatment is required when the platelet count is below 20 to 30 x 10(9)/L in the first or second trimester, if there is bleeding of if an intervention is required. Thus, platelet counts are monitored frequently during pregnancy. In the third trimester, the platelet count is maintained at 50 to 80 x 10 (9)/L to ensure that stable patients can receive neuraxial (epidural or spinal) anesthesia. The ability to receive neuraxial anesthesia is decided in consultation with the anesthesiologist. Thus, platelet counts are monitored frequently during pregnancy. If a high platelet count cannot be maintained in the third trimester, other methods of analgesia (pain control) will be used. The anesthesiologist will discuss alternate methods for pain if required.

How is ITP treated in pregnancy?

Treatment for ITP is aimed to maintain a safe platelet count during pregnancy and at the time of delivery as thrombocytopenia often resolves after delivery. Corticosteroids and intravenous immune globulin (IVIG) are the commonly used treatment modalities for ITP during pregnancy. Each has its advantages and potential side-effects which are routinely discussed at clinic appointments. Other treatments that may be required are individualized.

How does ITP affect the newborn?

A pregnancy with ITP may result in temporary thrombocytopenia in the newborn. Ten to 30% of newborns may have platelet counts less than 50 x 10(9)/L. The newborn will have the platelet number checked from the cord and within 24 to 48 hours after delivery. Newborns may require treatment for low platelet numbers.

Does ITP affect delivery?

The type of delivery is generally not affected by ITP (a Caesarean section is not required because of ITP). Because of the possibility of low platelets in the newborn, interventions that may increase the risk of bleeding in the newborn are not recommended (for example use of vacuum assisted delivery).

Special Pregnancy Program

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Fetal Medicine: 416-586-4800 x 7756
Fax: 416-586-3216

Maternal Medicine: 416-586-4800 x 7000
Fax: 416-586-5109

Main clinic hours: Monday to Friday, 8am to 4pm

Prenatal Diagnosis & Medical Genetics

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phone: 416-586-4800 x 4523
fax numbers:
416-586-4723 or 416-586-8384

Perinatal Mental Health

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Phone: 416-586-4800 x 8325
Fax: 416-586-8596