8/25/2023 0 Comments Yen timingHowever, the few studies that assessed associations with pregnancies and breastfeeding for BRCA1/2 mutation carriers have reported inconsistent results, ranging from studies supporting a decreased risk from FTP ( 13, 14) to studies supporting no association ( 15) to studies supporting an increased risk ( 16). Given the earlier age at which BC risk increases for women carrying a BRCA1 or BRCA2 ( BRCA1/2) mutation, it is important to know whether the BC risk for carriers is modified by the number and timing of their pregnancies and/or by breastfeeding. Thus, in addition to being related to long-term risk reduction, breastfeeding might mitigate a short-term increase in BC risk after FTP ( 10). While FTPs are associated with a reduced BC risk in the long-term, a short-term increase in BC risk has been consistently observed for women following an FTP ( 6–8), which may be reduced by breastfeeding ( 4, 9). The consistent association between the number of pregnancies and long-term reduction in BC risk is restricted to FTPs ( 3–5), as incomplete pregnancies (IP) have not been associated with BC risk. For women in the general population, it is well established that those who had their first full-term pregnancy (FTP) at a young age (<30 years) have a lower risk of BC than nulliparous women or women who had their first FTP after age 30 years additional FTPs are associated with even lower risks ( 2). Women carrying mutations in BRCA1 or BRCA2 are at high risk of developing breast cancer (BC) and ovarian cancer with cumulative BC risks to 80 years of 72% (95% CI = 65% to 79%) and 69% (95% CI = 61% to 77%) for BRCA1 and BRCA2 mutation carriers, respectively ( 1). For BRCA2 mutation carriers, being parous was associated with a 30% increase in BC risk (HR c = 1.33, 95% CI = 1.05 to 1.69), and there was no apparent decrease in risk associated with multiparity except for having at least 4 FTPs vs. Relative to being nulliparous, uniparous BRCA1 mutation carriers were at increased BC risk in the prospective analysis (prospective hazard ration = 1.69, 95% CI = 1.09 to 2.62). 0001) and increasing duration of breastfeeding was associated with decreased BC risk (combined cohort P trend = .0003). For BRCA1 mutation carriers, there was no overall association with parity compared with nulliparity (combined hazard ratio = 0.99, 95% confidence interval = 0.83 to 1.18).
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