Melbye M, Wohlfahrt J, Olsen J H, Frisch M, Westergaard T, Helweg-Larsen K, Andersen P K
Department of Epidemiology Research, Danish Epidemiology Science Center, Statens Serum Institut, Copenhagen, Denmark.
N Engl J Med. 1997 Jan 9;336(2):81-5. doi: 10.1056/NEJM199701093360201.
It has been hypothesized that an interrupted pregnancy might increase a woman's risk of breast cancer because breast cells could proliferate without the later protective effect of differentiation.
We established a population-based cohort with information on parity and vital status consisting of all Danish women born from April 1, 1935, through March 31, 1978. Through linkage with the National Registry of Induced Abortions, information on the number and dates of induced abortions among those women was combined with information on the gestational age of each aborted fetus. All new cases of breast cancer were identified through linkage with the Danish Cancer Registry.
In the cohort of 1.5 million women (28.5 million person-years), we identified 370,715 induced abortions among 280,965 women (2.7 million person-years) and 10,246 women with breast cancer. After adjustment for known risk factors, induced abortion was not associated with an increased risk of breast cancer (relative risk, 1.00; 95 percent confidence interval, 0.94 to 1.06). No increases in risk were found in subgroups defined according to age at abortion, parity, time since abortion, or age at diagnosis of breast cancer. The relative risk of breast cancer increased with increasing gestational age of the fetus at the time of the most recent induced abortion: <7 weeks, 0.81 (95 percent confidence interval, 0.58 to 1.13); 7 to 8 weeks, 1.01 (0.89 to 1.14); 9 to 10 weeks, 1.00 >12 weeks, 1.38 (1.00 to 1.90) (reference category, 9 to 10 weeks).
Induced abortions have no overall effect on the risk of breast cancer.
有假设认为，中断妊娠可能会增加女性患乳腺癌的风险，因为乳腺细胞可能会在没有后期分化保护作用的情况下增殖。
我们建立了一个基于人群的队列，其中包含生育情况和生命状态信息，该队列由1935年4月1日至1978年3月31日出生的所有丹麦女性组成。通过与国家人工流产登记处的关联，这些女性的人工流产次数和日期信息与每个流产胎儿的孕周信息相结合。所有乳腺癌新病例均通过与丹麦癌症登记处的关联得以识别。
在这个150万女性的队列（2850万人年）中，我们在280965名女性（270万人年）中识别出370715次人工流产，以及10246名乳腺癌患者。在对已知风险因素进行调整后，人工流产与乳腺癌风险增加无关（相对风险，1.00；95%置信区间，0.94至1.06）。在根据流产时年龄、生育情况、流产后时间或乳腺癌诊断时年龄定义的亚组中，未发现风险增加。随着最近一次人工流产时胎儿孕周的增加，乳腺癌的相对风险也增加：<7周，0.81（95%置信区间，0.58至1.13）；7至8周，1.01（0.89至1.14）；9至10周，1.00；>12周，1.38（1.00至1.90）（参照类别，9至10周）。
人工流产对乳腺癌风险没有总体影响。
