Intravenous Immunoglobulin (IVIG) can prevent severe blood platelet decreases (thrombocytopenia) in pregnancies complicated with fetal and neonatal alloimmune thrombocytopenia (FNAIT), but its efficacy can vary from pregnancy to pregnancy, according to a recently published study in Ultrasound in Obstetrics and Gynecology.
“In conclusion, our study shows that a good response to IVIG in one FNAIT-affected pregnancy does not guarantee the same response in subsequent pregnancies,” the authors wrote.
FNAIT is a rare condition where maternal antibodies target fetal platelets, potentially causing life-threatening bleeding. In most cases it is caused by the human platelet antigen (HPA)-1a. Despite its clinical significance, routine screening for FNAIT is not performed, Therefore, diagnosis usually occurs after complications arise.
Standard antenatal treatment includes weekly IVIG, with or without corticosteroids, initiated between 18–24 weeks of gestation. To further assess the efficacy of IVIG over several pregnancies the researchers conducted a retrospective cohort study including 225 pregnancies in 91 women diagnosed with FNAIT between 1992 and 2024. Of these, 121 pregnancies were treated with IVIG.
Among the IVIG-treated pregnancies, 82% demonstrated a good response, defined as absence of intracranial bleeding (ICH) and platelet count ≥50,000/μL (normal value: 150.000) at birth.
The median platelet count in responders was 172,000/μL, compared to 27,000/μL in non-responders. No cases of ICH occurred among treated pregnancies. The authors observed that on-responders had more severe thrombocytopenia in previous pregnancies and required earlier and longer treatment courses.
An analysis of 11 women with at least three IVIG-treated pregnancies showed inconsistent responses. In some cases, good responses in one pregnancy were followed by poor outcomes in the next, suggesting that response to IVIG may not be predictable.
The study highlights that while IVIG remains the cornerstone of FNAIT prevention, its efficacy is not absolute and varies even within the same patient. Factors such as HPA type and disease severity influence treatment outcomes.
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