Vachirasrisoontra, C., Anansakunwat, W., Suthantikorn, C., & Prichakas, P. (2017). Second Trimester Prenatal Screening for Down Syndrome in Thai Pregnant Women Using Alpha-fetoprotein and Free Beta-hCG. Thai Journal of Obstetrics and Gynaecology, 15(2), 69–77. retrieved from https://he02.tci-thaijo.org/index.php/tjog/article/view/82684