D., M., S. R., and M. R. “Serum β-Hcg Levels Between 12 to 20 Weeks of Gestation in Prediction of Hypertensive Disordrers of Pregnancy”. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, vol. 6, no. 8, July 2017, pp. 3347-51, doi:10.18203/2320-1770.ijrcog20173263.