Objective: The purpose of this study was to assess cost benefits of prenatal screening test for Down syndrome in developing countries (like Thailand) in order to inform OB/GYN clinical practice and medical/public health policy).Methods: A decision tree model was developed to analyze cost-benefits of the two screening modalities versus conventional screening test as base case. The first screening modality was universal Thai NIPT (Thai Non-invasive Prenatal Test) and the second was contingent Thai NIPT. Input parameters related to clinical values and costs were obtained from both primary and secondary sources for Thai population. One-way analysis and probabilistic sensitivity analysis were performed to evaluate uncertainty surrounding model parameters.Results: Based on the societal perspective, performing universal Thai NIPT and contingent Thai NIPT yielded differences of incremental benefit to incremental cost of -4,472 to -3,784 Thai Baht (-127.77 to -108.11 US$) and 396 to 1,085 (11.31 to 31.00 US$) when each was compared to conventional tests. The ratio of incremental benefit to incremental cost was 0.03 to 0.14 for universal Thai NIPT, respectively and thus cost was saved for contingent Thai NIPT. Conclusion:Applying Thai NIPT as the first line of screening for Down syndrome might be cost beneficial if the price was around 4,047 to 4,795 Thai Baht or US$ 115.63 to 137.00 per test. The contingent Down syndrome screening tests by offering the conventional tests first, then followed by Thai NIPT before performing the invasive screening test which seems to be a cost beneficial alternative approach. Currently, there are three methods of NIPT: Shortgun (genomewide) massively parallel sequencing (s-MPS), targeted (t-MPS) and single nucleotide polymorphism (SNP) methods. NIPT is much more accurate than the conventional tests. Previous study reported the Down syndrome detection rate of primary NIPT for all pregnant women is 6-14% higher than the conventional tests with 45-fold FPR (false positive rate.) reduction from meta-analysis [6]. However, the NIPT is still more costly. In order to inform OB/GYN clinical practice and medical/public health policy, this study was conducted to assess the cost benefit of prenatal screening test for Down syndrome with non-invasive prenatal test in developing countries (like Thailand). The Thai NIPT, a not-for-profit service, has been established and wholly processed at Ramathibodi Hospital, Thailand by using s-MPS since 2014 [7]. Cost Benefit Analysis of Prenatal MethodsThis design was a cross-sectional study and cost benefit analysis,