The objective of the study was to examine whether secular trends in parity explain the increase in breast cancer incidence among US women aged 25 to 39 years from 1935 to 2015. The study concluded that breast cancer incidence for women aged 25 to 39 years has been significantly increasing since the 1930s and cannot be attributed to changes in parity over time.


  1. Johnson  RH, Chien  FL, Bleyer  A.  Incidence of breast cancer with distant involvement among women in the United States, 1976 to 2009.  JAMA. 2013;309(8):800-805.

  2. Oeffinger  KC, Fontham  ET, Etzioni  R,  et al; American Cancer Society.  Breast cancer screening for women at average risk: 2015 guideline update from the American Cancer Society.  JAMA. 2015;314(15):1599-1614.

  3. Kehm  RD, Yang  W, Tehranifar  P, Terry  MB.  40 Years of change in age- and stage-specific cancer incidence rates in US women and men.  JNCI Cancer Spectr. 2019;3(3):pkz038.


Women's Health  



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