Relation between age of mothers with breast cancer and sex of their children

In a consecutive series of 150 women with breast cancer 122 had borne one or more children. Sixty-two patients were aged below 55 years at diagnosis (group A) and 60 were 55 years or older (group B). In group A 91 out of 153 children (59%) were boys compared with 48 out of 141 (34%) in group B (p=0 000007). In group A 54 of the 62 patients (87%) had given birth to one or more boys compared with 35 of the 60 (58%) in group B (p=0 0003). The mean age at diagnosis in mothers of two or more boys was 49 0 years, in those of one boy 55-2 years, and in those of only girls 61 0 years. The differences between each of the mean ages was significant. The mean age at diagnosis in 28 nulliparous patients was 57-7 years. There was no significant correlation between the number of female pregnancies and age at diagnosis. These results suggest that in women liable to develop breast cancer male pregnancies are associated with an early onset of the disease. © 1980, British Medical Journal Publishing Group. All rights reserved.