To the Editor.
—Dr Newcomb and colleagues1 observed a weakly positive association between abortion and risk of breast cancer. The increase in risk of breast cancer was not significantly different if the abortion was induced or spontaneous.An allele of the estrogen receptor gene, called the B' allele, contains a silent mutation in codon 87, part of the receptor's B domain.2 Because of the association reported of the B' allele, spontaneous abortion, and estrogen receptor—positive breast cancer,3 a preliminary case-control study was performed to estimate the risk of breast cancer in women with the B' allele.4 Among BB' heterozygote women with estrogen receptor—positive breast cancers (23 cases, 27 controls), the risk of breast cancer was associated with a history of spontaneous abortion; the age-adjusted odds ratios were 4.1 (95% confidence interval [CI], 0.95-18) after 1 spontaneous abortion and 9.7 (95% CI, 1.6-61) after 2 or more spontaneous abortions. No
Lehrer S. Pregnancy Termination and Risk of Breast Cancer. JAMA. 1996;276(1):31. doi:10.1001/jama.1996.03540010033024