Thrombocytopenia: A reduced level of platelets, a specialized kind of blood cell.
Normal Lab Values: <150 x 10 9/L. This value is the same regardless of age.
Thrombocytopenia is another lesser-known complication of HDFN, affecting 26% of fetuses 1 and infants 2. Thrombocytopenia can develop with any antibody including and not limited to: anti-D, anti-K, anti-c, anti-E. The child’s body is so busy producing red blood cells to compensate for the ones destroyed by the antibodies, that it simply does not produce other blood cells including white blood cells (neutrophils), and platelets (thrombocytes) 3. This can lead to thrombocytopenia – a low level of platelets. Risk factors include IUTs, small for gestational age, and lower gestational age at birth. Hydropic infants are more likely to be thrombocytopenic, though thrombocytopenia occurs in non-hydropic infants as well. Infants with thrombocytopenia experience bruising and bleeding easier than other infants. For the majority of infants, this is just monitored with occasional blood draws and diligence about bumps and bruises. In severe cases, platelet transfusions are utilized. “Thrombocytopenia is an independent risk factor for perinatal mortality. Mortality in fetuses that were severely thrombocytopenic and severely hydropic was 67%.” 1
For additional articles about HDFN and thrombocytopenia, see our additional reading by topic page.
In addition to thrombocytopenia due to HDFN and red blood cell antibodies, there is also a similar condition called fetal and neonatal alloimmune thrombocytopenia (FNAIT). In this disease, the mother makes antibodies against antigens on her baby’s platelets (instead of red blood cells). Just like with HDFN, platelet antibodies can cross the placenta and destroy fetal platelets. This leaves the fetus or newborn at risk of hemorrhaging into major organs such as the brain, stomach, spinal cord, kidneys, liver, and skin. Babies with FNAIT are at risk of suffering lifelong disabilities or dying. For more information about FNAIT, please contact NAIT Babies and see this leaflet from the NHS on platelet antibodies in pregnancy.