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Induced abortion doesn't increase risk of developing cancer, study shows

Melissa Mitchell, News Editor

Released 12/1/2006

CHAMPAIGN, Ill. — A new study that tracked the health of thousands of female textile workers in China indicates that women who have had an abortion do not have an increased risk of developing cancer.

Principal investigators Karin Rosenblatt, a professor of kinesiology and community health at the University of Illinois at Urbana-Champaign, and David B. Thomas, a member in the Fred Hutchinson Cancer Research Center and professor at the University of Washington in Seattle, said their research team looked at possible associations between abortion and all cancers combined and a dozen specific types of cancer – including breast cancer – and concluded that “the risk of all cancers combined was no greater in women who had had an induced abortion than in women who had not.”

The researchers assessed cancer risks among women reporting one or more induced abortions. Cancer types profiled included those that might be associated with hormonal causation (breast, colon, gallbladder, liver, ovary, thyroid, uterine cervix and uterine corpus), and those (lung, pancreas, rectum and stomach) that commonly occur within the general population in China.

The study’s 267,400 participants, employed at 500 different textile-industry plants, were cohorts included in a broader, randomized trial designed to assess the effectiveness of breast self-examinations. Between 1989 and 1991, the workers completed a baseline questionnaire that determined major risk factors for breast cancer, contraceptive use and induced abortions, and were actively monitored for the occurrence of cancer until July 2000.

Among the women surveyed who did not develop cancer, 53.2 percent reported ever having had an abortion, and 37.3 percent, 13.1 percent and 2.7 percent indicated they had had one, two and three or more, respectively.

“One of the things that is different about our study is that it is a cohort study within this large, randomized trial,” Rosenblatt said. “It’s also the only study that has looked at multiple cancer sites.”

While some previous case-control studies have suggested a causal link between abortion and breast cancer, Rosenblatt said such studies – which compare actual cases against a control group – are prone to reporting bias.

“All interview-based case-control studies have the potential for bias for a variety of reasons, including memory lapses of participants,” she said. Self-reported data also may be flawed in studies involving potentially sensitive or politically charged topics such as abortion.

“In the United States, despite its legal status, abortion is not looked at favorably by many persons,” Rosenblatt said. Because of the social stigma still attached to abortion, many community health researchers suspect control subjects tend to under-report when providing personal-history data, she said.

Rosenblatt and Thomas noted that their negative findings with respect to a link between abortion and breast cancer are similar to those from a large pooled analysis of data from 13 cohort studies (that included earlier results from the present study).

Also notable among the data collected for this study are findings suggesting induced abortions may actually reduce the risk of endometrial cancer among women in China, Rosenblatt said.

“We don’t know whether the results are applicable to other populations. We need more studies,” Rosenblatt said.

Results of the present study, supported by grants from the National Cancer Institute, will appear in the December issue of the journal Cancer Causes and Control.

Co-authors with Rosenblatt and Thomas are Dao Li Gao, Roberta M. Ray, Michelle R. Rowland, Zakia C. Nelson, Karen J. Wernli and Wenjin Li.