IUD Does Not Increase Infertility, Study Shows
The use of a copper intrauterine device is not associated with an increased risk of tubal infertility among women who have never been pregnant, as previously believed, according to a study published in this week's New England Journal of Medicine. In fact, exposure to chlamydia is the greater predictor of tubal infertility, researchers from Family Health International in Research Triangle Park, N.C., report. Dr. David Hubacher and colleagues interviewed 1,895 women at three Mexico City hospitals about their previous contraceptive use, sexual history and history of genital tract infections (Hubacher et al., NEJM, 8/23). Mexico was chosen as the study site because IUD use is "more common" there than in the United States (Rubin, USA Today, 8/23). Researchers also gave the women a blood test to check for antibodies to chlamydia. The women were then divided into three groups: 358 with primary infertility who had tubal blockages, 953 women with primary infertility who did not have tubal occlusion and 584 pregnant women controls. None of the women had experienced a previous pregnancy, laparoscopy or tubal sterilization.
The researchers found that infertile women who had previously used copper IUDs had a 1.0 odds ratio that the tubal occlusion was associated with IUD use, compared to those women who also experienced infertility but did not have a tubal occlusion. The odds ratio when compared to the pregnant women was 0.9. Only 6.4% of the women with tubal occlusion had used a copper IUD, while 6.0% of the infertile women without tubal blockage had also used a copper IUD. However, 38.3% of the infertile women with tubal occlusion and 35.4% of the infertile women who did not have tubal occlusion tested positive for antibodies to chlamydia, leading the researchers to conclude that "[t]ubal infertility was not associated with the duration of IUD use, the reason for removal of the IUD or the presence or absence of gynecologic problems related to its use. The presence of antibodies to chlamydia was associated with infertility." The researchers noted that previous studies did not test for chlamydia and therefore may have mistakenly concluded that the IUDs were the cause of the infertility (NEJM, 8/23).
IUDs are used by 106 million women worldwide and are the "most prevalent" form of reversible contraception, but only 1% of American women of reproductive age use IUDs as a contraceptive option, largely due to previous reports that the devices cause pelvic infections that can lead to infertility. The device, a T-shaped plastic piece wrapped in copper wire, works to prevent pregnancy by "slowly" releasing copper into the uterus to irritate the lining and alter fluids in the uterus and fallopian tubes. Several newer IUDs release hormones to interfere with ovulation instead of copper. In 1974, sales of the Dalkon Shield, manufactured by A.H. Robins & Co., were halted after complaints of "painful, sexually transmitted uterine infections" that were blamed for infertility and "at least" 18 deaths. The company paid about $3 billion to 200,000 women after facing numerous lawsuits and was forced to declare bankruptcy (Johnson, AP/Philadelphia Inquirer, 8/23). The controversy "torpedoed" the American IUD market, which saw use decline from 10% in 1970 to 7.1% in 1982, and to 0.8% in 1995, according to a government survey (Guidera, Wall Street Journal, 8/23).