Pregnancy Labor and Birth. Office on Women’s Health, U.S. Department of Health and Human Services. 1 February 2017 [15 July 2017]. (原始内容存档于2017-07-28). 本文含有此來源中屬於公有领域的内容。
Pregnancy Labor and Birth. Office on Women’s Health, U.S. Department of Health and Human Services. 1 February 2017 [15 July 2017]. (原始内容存档于2017-07-28). 本文含有此來源中屬於公有领域的内容。