Fetal thrombocytopaenia refers to an abnormally low platelet count in the fetus. The acceptable normal range for a fetal platelet count is similar to adults and do not vary significantly with gestation age. The lower limit for cut off is therefore usually taken as:
- 150,000/uL for thrombocytopaenia and
- 50,000/uL for severe thrombocytopaenia
It is most often caused by maternal alloantibodies against fetal platelets crossing the placenta and resulting in platelet destruction. This condition, known as fetal and neonatal alloimmune thrombocytopenia (FNAIT) is considered a platelet equivalent of Rh isoimmunisation 5.
Other causes include:
Recognised associations include:
- radial ray anomalies
- placental chorioangioma 3
- maternal autoimmune thrombocytopaenic purpura: the fetus tends to develop thrombocytopaenia in ~40-70% of cases 1.
- 1. Merz E, Bahlmann F. Ultrasound in obstetrics and gynecology. Thieme Medical Publishers. (2005) ISBN:1588901475. Read it at Google Books - Find it at Amazon
- 2. Porcelijn L, Van den akker ES, Oepkes D. Fetal thrombocytopenia. Semin Fetal Neonatal Med. 2008;13 (4): 223-30. doi:10.1016/j.siny.2008.02.008 - Pubmed citation
- 3. Kirkpatrick AD, Podberesky DJ, Gray AE et-al. Best cases from the AFIP: Placental chorioangioma. Radiographics. 27 (4): 1187-90. doi:10.1148/rg.274065207 - Pubmed citation
- 4. Rodeck CH, Whittle MJ. Fetal medicine, basic science and clinical practice. Elsevier Health Sciences. (2008) ISBN:0443104085. Read it at Google Books - Find it at Amazon
- 5. Nyberg DA, McGahan JP, Pretorius DH. Diagnostic imaging of fetal anomalies. Lippincott Williams & Wilkins. (2003) ISBN:0781732115. Read it at Google Books - Find it at Amazon