low platelets and pregnancy

Last reviewed 01/2018

Seek expert advice.

Thrombocytopenia is defined as a platelet count below 150 × 10^9/l

  • occurs in approximately 10% of pregnant women

Causes to consider include:

  • pregnancy-associated thrombocytopaenia - this condition is self-limiting and results in a mild thrombocytpaenia (platelet count above 70x 10^9/L) (also known as benign gestational thrombocytopaenia) (1)
    • most prevalent cause of thrombocytopenia in pregnancy
    • accounts for about 75% of cases of thrombocytopenia during pregnancy
    • thrombocytopaenia (especially during the third trimester) - platelet count returns to normal within 12 weeks of delivery
  • autoimmune thrombocytopaenia purpura (immune thrombocytopaenic purpura)
    • caused by platelet destruction in the reticular endothelial system, due to platelet auto-antibodies against several platelet membrane glycoprotein complexes
    • moderate to severe decrease in the platelet count
    • approximately 5% of cases of thrombocytopenia in pregnancy
    • requires monitoring during pregnancy and after delivery, and may require treatment - there is a higher risk of maternal hemorrhage when the platelet count is low
    • minor risk of thrombocytopenia in the newborn
  • preeclampsia and HELLP (Hemolysis, elevated liver enzymes and low platelet count) syndrome
    • cause of thrombocytopenia in pregnancy in about 20% of cases
    • maternal platelet count returns to normal within 3-5 days of delivery
  • rarer causes of thrombocytopenia during pregnancy, include thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), disseminated intravascular coagulation (DIC), systemic lupus erythematosus (SLE), anti-phospholipid antibodies syndrome (APLA),
    • thrombocytpaenia associated with haemolytic uraemic syndrome or thrombotic thrombocytopaenia purpura - it is now believed that thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome represent a spectrum of disease
  • decreased production of platelets - this occurs in effective megakaryopoiesis (e.g. folate deficiency, vitamin B12 deficiency) and in generalised diseases of the bone marrow that lead to reduced platelet production (e.g. disseminated cancer, aplastic anaemia)
  • consider other causes of thrombocytopaenia - see linked item for more details

Reference:

  1. Parnas M et al. Moderate to severe thrombocytopenia during pregnancy. Eur J Obstet Gynecol Reprod Biol. 2006 Sep-Oct;128(1-2):163-8