MacMahon B, Purde M, Cramer D, Hint E
J Natl Cancer Inst. 1982 Nov;69(5):1035-8.
Information on reproductive history was obtained from 362 urban breast cancer patients attending the oncological dispensaries at Tallinn and Tartu, Estonian Republic, and from 694 urban women participating in gynecologic screening programs offered by the same centers. The 2 groups were compared by means of Mantel-Haenszel and logistic regression procedures to estimate age-adjusted odds ratios. Women whose first birth occurred before 20 years of age had a breast cancer risk less than one-third the risk of nulliparous women. Risk increased with increase in age at first birth (AFB) but remained below 1.0 (relative to nulliparae), even in the highest AFB categories. The fertility rate in Estonia during the period of this study was relatively low, which facilitated an evaluation of the effect of births subsequent to the first. After adjustment for AFB, it appeared that in this population subsequent births had a protective effect additional to that conferred by the first birth. Moreover, for women who had only 2 children, the age at the time of birth of the second child was a determinant of that effect. Compared to nulliparous women, the breast cancer odds ratio for uniparous women who had their child before age 25 was 0.62, and the ratio for duoparous women who had both their children under that age was 0.18. Neither lactation nor menarche was a risk factor for breast cancer in this pouplation.
生殖史信息取自爱沙尼亚共和国塔林和塔尔图肿瘤防治所的362名城市乳腺癌患者，以及参与同一中心提供的妇科筛查项目的694名城市女性。通过Mantel-Haenszel法和逻辑回归程序对两组进行比较，以估计年龄调整后的比值比。首次生育发生在20岁之前的女性患乳腺癌的风险不到未生育女性的三分之一。风险随着首次生育年龄（AFB）的增加而增加，但即使在最高的AFB类别中，仍低于1.0（相对于未生育女性）。在本研究期间，爱沙尼亚的生育率相对较低，这便于评估首次生育后后续生育的影响。在对AFB进行调整后，似乎在该人群中，后续生育除了首次生育所带来的保护作用外，还有额外的保护作用。此外，对于只有两个孩子的女性，第二个孩子出生时的年龄是该影响的一个决定因素。与未生育女性相比，在25岁之前生育一个孩子的单胎女性患乳腺癌的比值比为0.62，在该年龄之前生育两个孩子的双胎女性的比值比为0.18。在这个人群中，哺乳和初潮都不是乳腺癌的危险因素。
