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