Abstract
Objective: Identify time-points when the elevated postpartum maternal breast cancer risk peaks. Methods: A case–control study nested within the Swedish Fertility Register included 34,018 breast cancer cases from the Swedish Cancer Register between 1961 and 1995. From the Fertility Register, 170,001 eligible subjects matched to the cases by age were selected as controls. Analysis contrasted risk between uniparous (7084 cases and 31,703 controls) and nulliparous (5411 cases and 22,580 controls) women and between biparous (13,239 cases and 65,858 controls) and uniparous women. Logistic regression analysis included indicator variables representing each year of age, ages at delivery, and time since delivery. Results: Comparing uniparous with nulliparous women the transient increase in maternal breast cancer risk peaked 5 years following delivery (odds ratio = 1.49, 95% confidence interval 1.01–2.20) and leveled off 15 years postpartum. Biparous women had a transient increase in risk that was lower at its peak than that of uniparous women, occurring about 3 years following second delivery. Conclusions: A time window of 5 years postpartum when maternal breast cancer risk is highest was observed. Establishing timing of peak transient increase in postpartum breast cancer risk may define the latent period required for pregnancy hormones in promoting progression of breast cells that have undergone early stages of malignant transformation.
Similar content being viewed by others
References
Bruzzi P, Negri E, La Vecchia, et al. (1988) Short term increase in risk of breast cancer after full term pregnancy. BMJ 297: 1096-1098.
Williams EMI, Jones L, Vessey MP, McPherson K (1990) Short term increase in risk of breast cancer associated with full term pregnancy. BMJ 300: 578-579.
Hsieh CC, Pavia M, Lambe M, et al. (1994) Dual effect of parity on breast cancer risk. Eur J Cancer 30A: 969-973.
Lambe M, Hsieh CC, Trichopoulos D, Ekbom A, Pavia M, Adami HO (1994) Transient increase in the risk of breast cancer after giving birth. N Engl J Med 331: 5-9.
Rosner B, Colditz GA (1996) Nurses' Health Study: log-incidence mathematical model of breast cancer incidence. J Natl Cancer Inst 88: 359-364.
Hsieh CC, Lan SJ (1996) Assessment of postpartum time-dependent disease risk in case-control studies: an application for examining age-specific effect estimates. Stat Med 15: 1545-1556.
Cummings P, Weiss NS, McKnight B, Stanford JL (1997) Estimating the risk of breast cancer in relation to the interval since last term pregnancy. Epidemiology 8: 488-494.
Heuch I, Albrektsen G, Kvale G (1999) Modeling effects of age at and time since delivery on subsequent risk of cancer. Epidemiology 10: 739-746.
Lunde AS, Lundeborg S, Lettenstro¨ m GS, et al. (1980) The Person-Number Systems of Sweden, Norway, Denmark, and Israel. Hyattsville, MD: National Center for Health Statistics. DHHS Publ. No. (PHS) 80-1358. Vital and Health Statistics, series 2, 84: 5-11.
Center for Epidemiology (1998) Cancer Incidence in Sweden 1995. Stockholm: Center for Epidemiology.
Armitage P, Berry G (1994) Statistical Methods in Medical Research, 3rd edn. Malden, MA: Blackwell Science, pp. 341-348.
Rothman KJ, Greenland S (1998) Modern Epidemiology, 2nd edn. Philadelphia, PA: Lippincott-Raven, pp. 392-394.
National Board of Health and Welfare (2000) Yearbook of Health and Medical Care 2000. Stockholm.
Hsieh CC, Trichopoulos D, Katsouyanni K, Yuasa S (1990) Age at menarche, age at menopause, height and obesity as risk factors for breast cancer: associations and interactions in an international case-control study. In J Cancer 46: 796-800.
Thompson, WD (1997) Age at and time since: modeling temporal aspects of exposure. Epidemiology 8: 471-473.
Cummings P, McKnight B, Weiss NS (2000) Modeling the effects of age at and time since delivery on subsequent risk of cancer. Epidemiology 11: 479-481.
Heuch I, Albrektsen G, Kvale G (2000) Modeling the effects of age at and time since delivery on subsequent risk of cancer. Epidemiology 11: 481.
Kelsey JL, Gammon MD, John EM (1993) Reproductive factors and breast cancer. Epidemiol Rev 15: 36-47.
Bernstein L, Depue RH, Ross RK, Judd HL, Pike MC, Henderson BE (1986) Higher maternal levels of free estradiol in first compared to second pregnancy: early gestational differences. J Natl Cancer Inst 76: 1035-1039.
Henderson BE, Feigelson HS (2000) Hormonal carcinogenesis. Carcinogenesis 21: 427-433.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Liu, Q., Wuu, J., Lambe, M. et al. Transient increase in breast cancer risk after giving birth: postpartum period with the highest risk (Sweden). Cancer Causes Control 13, 299–305 (2002). https://doi.org/10.1023/A:1015287208222
Issue Date:
DOI: https://doi.org/10.1023/A:1015287208222