Pregnancy related protection against breast cancer depends on length of gestation.
In a prospective study of 694 657 parous women in Norway, 5474 developed breast cancer after their first birth. If the first pregnancy lasted less than 32 weeks, the risk was 22% (95% confidence interval, -3% to 53%) less than after a pregnancy of 40 weeks or more, with a significant declining trend in risk (P for trend=0.02).
Department of Community Medicine and General Practice, The Norwegian University of Science and Technology, Trondheim, Norway. Lars.Vatten@medisin.ntnu.no
L J
LJ
Vatten
P R
PR
Romundstad
D
D
Trichopoulos
R
R
Skjaerven
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy / Q000502:physiology*; D011446:Prospective Studies; D013997:Time Factors