What is fetal and neonatal alloimmune thrombocytopenia (NAIT)?
Fetal and neonatal alloimmune thrombocytopenia (NAIT) is a condition where a fetus or newborn experiences severe thrombocytopenia (low platelet count). NAIT occurs when the mother's immune system develops antibodies against antigens on the fetal platelets, which are inherited from the father and different from those present in the mother. These antibodies cross the placenta and can cause severe thrombocytopenia in the fetus. NAIT has been considered to be the platelet counterpart of Rh Hemolytic Disease of the Newborn (RHD). The incidence has been estimated at 1/800 to 1/1,000 live births. The spectrum of the disease may range from mild thrombocytopenia to life-threatening bleeding.
Last updated: 6/6/2011
What is the risk of fetal and neonatal alloimmune thrombocytopenia (NAIT) happening in future pregnancies?
The current management of subsequent pregnancies after a previous child affected with NAIT is aimed at preventing severe thrombocytopenia during pregnancy and delivery. After a mother has had a baby with NAIT, there is a high rate of recurrence and increased severity of the fetal thrombocytopenia in successive pregnancies. This risk, however, depends on the father's genetic status for the antigen. The father can either have one copy of a particular gene mutation that causes the platelet antigen to form (called a heterozygote) or two copies (called a homozygote). If the father is a heterozygote, there is a 50% chance that he will pass on this condition to his child. Fathers that are homozygotes have a 100% chance of passing on this condition. In the case of a heterozygote father or if the paternity is uncertain, the genetic status of the fetus should be determined through prenatal testing.
Regardless of whether the genetic status of the father is known, the mother should be offered therapy during her pregnancy, such as high doses of intravenous immunoglobulin administered once a week. The fetus can also be given weekly platelet infusions with antigen negative platelets. However, management of high-risk pregnancies is still a matter of discussion.
Last updated: 6/6/2011
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