Decreased platelets during pregnancy

Decreased platelets during pregnancy, also known as Gestational Thrombocytopenia, is a blood disorder that can affect up to 15% of pregnant women. In this condition the platelet count decreases below 100,000/mm3. Early diagnosis is important in order to treat the mother as soon as possible, with the aim of reducing the effects on the fetus.

Why do platelets drop in pregnancy?

Low platelets or thrombocytopenia can affect up to 15% of all pregnancies, being the second cause of hematological alteration in this population group, surpassed only by anemia. We speak of thrombocytopenia when the platelet count falls below 100,000/mm3.

Origin of the decrease in platelets or thrombocytopenia

This phenomenon may be related to pre-existing conditions present in women of childbearing age, such as primary immune thrombocytopenia (PIT) and systemic lupus erythematosus (SLE). Also in pregnancy disorders, such as Gestational Thrombocytopenia or HELLP Syndrome, which is a disorder typical of the third trimester of pregnancy, often related to processes of gestosis or hypertension during pregnancy.

HELLP Syndrome is caused by an alteration of the microvasculature of the patient that produces, among other things, an accelerated destruction of blood cellularity, with an excessive increase of transaminases, hemolytic anemia with the presence of broken red blood cells in the study of the blood smear called schistocytes. It is a syndrome that represents a hematologic emergency, given the clinical complications it can cause to both the mother and the fetus.

As mentioned, up to 15% of pregnancies may have decreased platelet counts. This is physiologically more evident during the third trimester of pregnancy, due to a dilutional mechanism coupled with accelerated platelet destruction when passing through the damaged surface of the placenta. In the case of multiple gestations, the decreased platelet count may be associated with an increase in thrombin production, which would cause an accelerated consumption of platelets. This is called gestational thrombocytopenia.

Incidence of Gestational Thrombocytopenia and Diagnosis

Gestational thrombocytopenia is considered a benign disorder, occurring incidentally in 5% of all pregnancies, and is the cause of up to 80% of the thrombocytopenias that may occur during pregnancy. It is diagnosed because the platelet count in blood tests, specifically the hemogram, ranges between 70,000 – 110,000/mm3 in almost 90% of cases.

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It is essential, as in any hematological process, to take a correct and structured clinical history of the patient, with special emphasis on family and personal history of thrombocytopenia, as well as previous pregnancies with thrombocytopenia during the course of the pregnancy. Physical examination for hemorrhagic lesions in the form of hematomas or petechiae is crucial for the diagnostic approach. Similarly, the finding of visceromegaly or enlargement of the liver or spleen is important, which may point to an underlying hemolytic problem, especially in the third trimester of gestation.

From the analytical point of view, both the obstetrician-gynecologist and the hematologist will request the appropriate biochemical or serological studies, as well as the analysis of the blood smear by the latter in search of morphological alterations in the hematological series that may point to one diagnosis or another.

It should be borne in mind that the diagnosis of Gestational Thrombocytopenia is made by ruling out other etiopathological processes that may cause a decrease in platelets during pregnancy.

Treatment of Gestational Thrombocytopenia and prognosis

There is no specific therapeutic indication for pregnant women with gestational thrombocytopenia. However, pregnant women should be monitored periodically by both the gynecologist and the hematology expert, depending on the platelet count of the patient. Natural transvaginal delivery is recommended, if other obstetric alterations do not contraindicate it. Epidural anesthesia can be safely administered with platelet counts above 70,000/mm3 , although everything will depend on the anesthesiologist’s assessment.

After pregnancy, platelet counts should be closely monitored to check for spontaneous resolution after delivery. However, there is a small group of postpartum women in whom thrombocytopenia may persist and develop immune thrombocytopenia (ITP).

It has also been observed that thrombocytopenia in subsequent pregnancies can reach up to 20% of pregnancies. Although the risk of neonatal thrombocytopenia is considered negligible, it is recommended that all neonates born to mothers with thrombocytopenia be followed by their pediatrician or neonatologist.