A national survey of U.K. specialists has found wide variation in how doctors manage fetal and neonatal alloimmune thrombocytopenia (FNAIT), according to results recently published in the British Journal of Hematology.
There is currently no routine antenatal screening for FNAIT in the U.K., meaning most cases are only detected after a baby is born with symptoms such as bruising or bleeding.
Once a woman has had an affected pregnancy, future pregnancies carry a higher risk of recurrence. The main preventive treatment is intravenous immunoglobulin (IVIg), a therapy derived from donated blood that works by reducing the harmful antibody response. Its use varies widely between countries, and UK-specific data on clinical practice have been scarce.
“This survey demonstrates the areas of both consistency and variation in UK practice, highlighting gaps in the evidence base and priorities for future research and guidelines development,” the authors wrote.
To map current practices, the authors surveyed specialists at 16 of 22 regional fetal medicine centers across England and Scotland using a series of scenario-based questions. Responses were collected between June and September 2024. Centers where more than one clinician responded were asked to reach a consensus before submitting their answers.
There was broad agreement on several points. Across all scenarios, strong consensus emerged around treating affected pregnancies with weekly IVIg at a dose of 1 g per kilogram of body weight. Specialists consistently favoured starting treatment earlier for higher-risk cases where a previous baby had experienced brain bleeding, compared with around 20 to 24 weeks for lower-risk pregnancies.
Fetal blood sampling and platelet transfusions directly into the womb, once common interventions, were broadly considered unnecessary. Nearly all respondents rated their confidence in managing FNAIT as high or very high.
However, variation emerged in other areas. There was no clear consensus on whether delivery should be by planned caesarean section or could follow standard obstetric practice. Specialists also differed on the use of corticosteroids.
Management of women who had a family history of FNAIT but no personal diagnosis was notably inconsistent. The management of pregnancies involving anti-HPA5b antibodies, a second type of immune protein implicated in FNAIT, whose role in causing harm remains scientifically disputed, was also uncertain.
The authors note that some areas of inconsistency reflect genuine gaps in the evidence, not just differences in clinical style. The evidence base for IVIg rests largely on observational studies and trials comparing different IVIg regimens rather than placebo-controlled trials, meaning its true effectiveness, particularly in lower-risk pregnancies, remains uncertain.
The ongoing FREESIA-1 trial, testing nipocalimab in FNAIT, represents the first rigorous test of this kind.
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