Objective: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) results from maternal platelet-directed antibodies which can cause severe intracranial haemorrhage (ICH) in fetuses and new-borns. Screening for human platelet antigen-1a (HPA-1a) directed antibodies during pregnancy could allow for timely intervention with antenatal treatment and prevent the occurrence of ICH. We aim to assess the cost-effectiveness of adding screening for anti-HPA-1a to the prenatal screening program. Design: A decision analysis model was developed. Setting: The Netherlands. Population: 171,713 pregnant women. Methods: Lifetime costs and effects of antenatal anti-HPA-1a screening with subsequent diagnostic and treatment interventions were compared to the current situation without screening in the Netherlands. Model parameters were based on literature and expert opinions. One-way-sensitivity analysis and probabilistic sensitivity analysis were performed. Main Outcome Measures: Incremental cost-effectiveness ratio (ICER). Results: Adding screening for HPA-1a antibodies to the current antenatal screening program of the Netherlands will lead to an additional cost of 4.7 million euro and a gain of 226 Quality-Adjusted Life Years (QALY) per year, indicating an ICER of \euro20,782 per QALY gained. One-way sensitivity analysis showed that the uncertainty around the incidence of ICH, lifetime costs of disabled children and the probability of having antibody quantitation >3.0 IU/ml at 20 weeks had the highest effect on the ICER. Conclusion: Antenatal HPA-1a screening might be cost-effective. To obtain more knowledge and thereby reduce the uncertainty on risk stratification, a pilot screening program is warranted. Funding: Sanquin

OBJECTIVE(S): to evaluate the severity of HDFN in subsequent pregnancies with RhD immunization and to identify predictive factors for severe disease. DESIGN: prospective cohort. SETTING: the Netherlands. POPULATION: nationwide selection of all pregnant women with RhD antibodies. METHODS: women with two subsequent RhD immunized pregnancies with RhD-positive children after antibodies were detected were included. MAIN OUTCOME MEASURE: the severity of HDFN in the first and subsequent pregnancy at risk. RESULTS: 62 RhD immunized women with a total of 150 RhD-positive children were included. The severity of HDFN increased significantly in the subsequent pregnancy (P<.001), although it remained equal or even decreased in 44% of women. When antibodies were already detected at first trimester screening in the first immunized pregnancy, severe HDFN in the next pregnancy was uncommon (22%), especially when no therapy or only non-intensive phototherapy was indicated during the first pregnancy (6%), or if the ADCC result remained <10%. Contrarily, women with antibodies detected during the first pregnancy of a RhD positive child (>= 27th week), most often before they had ever received RhIg prophylaxis, were most prone for severe disease in a subsequent pregnancy (48%). CONCLUSION(S): RhD-mediated HDFN in a subsequent pregnancy is generally more severe than in the first pregnancy at risk and can be estimated using moment of antibody detection and severity in the first immunized pregnancy. Women developing antibodies in their first pregnancy of a RhD-positive child are at highest risk of severe disease in the next pregnancy.