The IUD and Tubal Infertility: Lifting the Fog?
In 1985, 2 large case-control studies[8,9] published in The New England Journal of Medicine described a doubling in the risk of tubal infertility associated with prior use of IUDs. The media gave these articles extensive coverage, and the conventional wisdom accepted these conclusions at face value. However, important findings in these 2 landmark studies went largely unnoticed. For example, in the Daling study from Seattle, Washington, women who had used only a copper device had no significant increase in the risk of tubal infertility, even if it had been removed because of problems. Similarly, in the Cramer study from the northeastern United States, the number of partners emerged as an important factor: women with only 1 sexual partner had no significant increase in the risk of tubal infertility, regardless of type of contraception use. The number of partners was important; the contraceptive used was not. An important limitation of both of these studies was that they did not have bacteriologic information.
In the first major study to address this question in 15 years, David Hubacher and his associates from Family Health International and the National Perinatology Institute in Mexico City, Mexico, have taken a fresh look at the old question of IUDs and tubal infertility. Hubacher began his presentation with an historic overview of the IUD in the United States over the past 3 decades. Between 1965 and 1995, the number of different IUDs on the market rose from 2 to 5 and then fell back to 2. The prevalence of IUD use rose dramatically and peaked at around 10% of women using contraception in the early 1970s, and it plummeted thereafter. He showed a strong temporal association between the number of published articles about IUDs and infertility and the decline in use. Indeed, other investigators have shown the powerful effect of adverse media blitzes on discontinuations of both IUDs and oral contraceptives.
Hubacher and his colleagues conducted a case-control study of tubal infertility at 3 hospitals in Mexico City. They designed the study to be large enough to have 90% power to detect an odds ratio of 2.0. That is, they made their study big enough to have a 90% chance of finding a 2-fold higher risk of tubal infertility associated with IUD use if it existed in the population. Cases included in the study had to be nulligravid, had to have had 12 months of unprotected coitus without pregnancy, and had to be having a hysterosalpingogram on the day of recruitment to the study. Hubacher and colleagues used 2 control groups: the standard control group consisted of primigravid women in the first or second trimester of pregnancy. The second control group included infertile women with causes other than tubal obstruction. Appealing features of the study were the inclusion of chlamydial antibody serology determinations for both cases and controls and the fact that all women in the study has used copper IUDs. No Dalkon Shields were included, unlike in the Daling and Cramer studies. The study was large: 359 cases with confirmed tubal infertility, 584 pregnant controls, and 953 infertile controls.
Use of a copper IUD had no effect on the risk of tubal infertility. The odds ratio (adjusted for the potential confounding effect of several factors) was 0.9 (95% CI 0.5-1.6) using pregnant controls and 1.0 (95% CI 0.6-1.7) using infertile controls. Stated alternatively, the risk estimates cluster tightly around unity, which means no association. The narrow confidence intervals indicate good precision: one can be fairly sure that the true risk for the entire population of women in Mexico City lies within these ranges.
A variety of risk factors were, however, linked with tubal infertility. These included number of sexual partners (similar to the Cramer study), prior abdominal operations, the presence of chlamydial antibodies, a prior diagnosis of pelvic inflammatory disease, and douching. By contrast, use of condoms was protective. These findings are all plausible and consistent with those reported in other literature; hence, these findings seem valid.
Dr. Hubacher's take-home message was 2-fold: prior infection with Chlamydia trachomatis (as judged by antibodies against Chlamydia) was significantly associated with tubal infertility. By contrast, use of a copper IUD was not. These 2 findings are complementary: STDs (chlamydial infection and gonorrhea, in particular), not plastic or copper, are the common causes of tubal infertility. When one controls for the confounding effect of prior STD exposure, the alleged increase in risk associated with IUD use (as found in the Daling and Cramer studies) disappears. This is important news for women and clinicians around the world.
Medscape Ob/Gyn. 2000;5(2) © 2000 Medscape
Cite this: Updates in Contraception From The XVI World Congress of the International Federation of Gynecology and Obstetrics - Medscape - Sep 20, 2000.