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Abstract

To evaluate the relationship between breast cancer risk and spontaneous and induced abortion, we conducted a detailed descriptive review of 32 epidemiologic studies that provided data by type of abortion and by various measures of exposure to abortion-number of abortions, timing of abortion in relation to first full-term pregnancy, length of gestation, and age at first abortion. Breast cancer risk did not appear to be associated with an increasing number of spontaneous or induced abortions. Our review also suggested that breast cancer risk probably was not related to the other measures of exposure to abortion, and probably did not differ by age or a family history of breast cancer. Finally, the data appeared to suggest a slightly increased risk among nulliparous women, but this tendency was based primarily on studies with a small number of nulliparous women who had had spontaneous or induced abortions. Definitive conclusions about an association between breast cancer risk and spontaneous or induced abortion are not possible at present because of inconsistent findings across studies. Future investigations should consider prospective designs, separate analyses of spontaneous and induced abortions, appropriate referent groups, and adequate adjustment for confounding and effect modification. Future investigations also should attempt to determine whether any increased risks reflect the transient increase in breast cancer risk hypothesized for full-term pregnancy or a causal relationship specific to spontaneous or induced abortion.

Pregnancy characteristics and maternal breast cancer risk: a review of the epidemiologic literature

“…Induced and spontaneous abortion, which reflect pregnancy interruption in early gestation (primarily first trimester), and breast cancer have been well studied [108, 109], but few studies have examined breast cancer and variation in gestational length for live births. Pregnancies that are shorter in duration during the third trimester have been hypothesized to increase breast cancer risk, due to a possible lack of full terminal differentiation of the mammary gland after elevated pregnancy hormonal levels [16, 110].…”

Induced abortion and breast cancer

“…In addition, we also performed the subgroup analysis based on different reproductive history to account for high heterogeneity among individual studies. Two epidemiological [ 44 , 45 ] reviews have pointed out that it would be most appropriate to separately compare the data from nulliparous and parous women. Infact, inclusion of parous women along with nulliparous may result in an increase in breast cancer risk for young women who have actually not had a full-term pregnancy due to their nulliparity and not because of incomplete pregnancy.…”

Association of pregnancy complications/risk factors with the development of future long-term health conditions in women: overarching protocol for umbrella reviews

“…Depression and anxiety disorders are common after miscarriage, stillbirth and preterm births 24–26. Studies have also identified pregnancy complications such as miscarriage and preterm birth are associated with future risk of breast cancer 27 28…”