Chanthasenanont, Athita, Tongta Nanthakomon, and Densak Pongrojpaw. 2012. “The Relationship between Maternal Age and Uterine Artery Doppler Flow During Second Trimester”. Thai Journal of Obstetrics and Gynaecology 20 (4). Bangkok, Thailand:173-78. https://he02.tci-thaijo.org/index.php/tjog/article/view/4685.