Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a disorder in which a pregnant mother passes on antibodies to the fetus that attack fetal platelets. Platelets are a type of blood cell necessary for forming clots. These are needed to stop internal and external bleeding.
Without adequate levels of platelets, a fetus is at significant risk of bleeding, including bleeding in the brain, otherwise known as intracranial hemorrhage.
FNAIT is typically suspected when a newborn demonstrates signs of bleeding, such as bruising or petechiae, which are tiny pink-purple spots on the skin.T o determine whether future pregnancies are at risk of FNAIT, a doctor may order a platelet typing test in the mother or in both the mother and father.
Maternal and paternal platelet typing tests may be necessary because, in FNAIT, maternal antibodies attack platelet antigens that are paternally inherited. Antigens are substances that trigger the formation of antibodies.
What is platelet typing?
Platelet typing in the context of FNAIT is a procedure to analyze the platelets in the mother and father to determine if there is an incompatibility between their respective human platelet antigen (HPA) types. It is this incompatibility that causes the mother’s body to produce antibodies that attack fetal platelets during pregnancy.
Read more about FNAIT causes and risk factors
Typically, fetal platelet typing is not performed due to the significant risks involved in drawing blood from a fetus. Instead, platelet typing is likely to be performed in an infant after birth. This allows doctors to check for compatibility for platelet transfusions, which are typically needed to address low platelet levels in FNAIT.
What should I expect?
Platelet typing is a simple procedure that involves a healthcare professional using a needle to withdraw blood from a vein, typically in the arm. The healthcare professional will first clean the area of the skin where blood will be withdrawn. Next, a tourniquet will be applied. After the blood-taking procedure, pressure is applied to the blood withdrawal site for a few minutes, after which bleeding should stop.
After results are available, your doctor will have further discussions with you on the best path forward. If a diagnosis of FNAIT is made, your doctor will be focused on ensuring that subsequent pregnancies are closely observed to prevent common complications. Your doctor will also be able to counsel you on some precautions to take if you become pregnant again in the future.
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