1. Mortality patterns - United States, 1989;MMWR Morb Mortal Wkly Rep,1992
2. Hoyert D.L., Miniño A.M. Maternal mortality in the United States: changes in coding, publication, and data release, 2018.
3. Hypertensive disorders and severe obstetric morbidity in the United States;Kuklina;Obstet Gynecol.,2009
4. Severe maternal morbidity among delivery and postpartum hospitalizations in the United States;Callaghan;Obstet Gynecol.,2012
5. Severe Maternal Morbidity in the United States, https://www.cdc.gov/reproductivehealth/maternalinfanthealth/severematernalmorbidity.html, Accessed June 1st, 2020.