A recent study published in Acta Obstetricia et Gynecologica Scandinavica found that infants with fetal and neonatal alloimmune thrombocytopenia (FNAIT) who are born to mothers with high anti-HPA-1a antibody levels may be at a higher risk of developing intracranial hemorrhage (ICH).
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition that affects 0.1% of pregnancies in which a pregnant mother’s immune system produces antibodies against the platelets of her fetus. This occurs when a fetus inherits platelet antigens from the father that are not compatible with the mother, typically involving a protein called human platelet antigen (HPA). The mother’s immune system recognizes the fetal platelets as foreign, attacking and destroying them, leading to low platelet levels (thrombocytopenia) in the fetus or newborn.
ICH is a severe, potentially life-threatening complication of FNAIT that occurs when the infant experiences bleeding in the brain. Affected individuals are susceptible to brain damage and neurological complications, but early detection can help reduce the risk of long-term effects.
Although many babies with FNAIT caused by the anti-HPA-1a antibody do not go on to develop ICH, pregnant women in most countries are still treated with intravenous immunoglobulin (IVIg) regardless of ICH risk. Therefore, the study authors sought to determine whether antibody levels can be used as a predictor of ICH risk to prevent the overuse of IVIg.
Read more about FNAIT signs and symptoms
The study included 69 pregnancies from clinic referrals throughout Norway and 146 pregnancies from a prior Norwegian screening study. All participants had HPA-1a alloimmunized pregnancies and were not treated with IVIg.
The results showed that among the pregnancies that resulted in FNAIT, anti-HPA-1a levels were significantly higher in those that were complicated by ICH. Platelet levels, however, did not vary widely between the groups; in fact, 82% of infants without ICH still had severe FNAIT.
The authors then used statistical methods to determine a potential antibody level cutoff that would identify pregnancies at risk of ICH. They ultimately chose a cutoff of 70 international units (IU) per milliliter.
With this value, 96.4% of infants without ICH were correctly classified as such. However, only 40% of those with ICH were correctly diagnosed, meaning this tool may be better for preventing false positives and avoiding unnecessary IVIg treatments.
“If other countries were to adopt a similar approach, it would result in a clear reduction in the number of pregnancies being treated with antenatal IVIg, thus reducing overtreatment,” the authors concluded.
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