Randomized field trial of vaginal douching, pelvic inflammatory disease and pregnancy
Rothman, K., Funch, D. P., Alfredson, T., Brady, J., & Dreyer, N. A. (2003). Randomized field trial of vaginal douching, pelvic inflammatory disease and pregnancy. Epidemiology, 14(3), 340-348.
Background. Several case-control studies have reported that women who use vaginal douche products are at increased risk for pelvic inflammatory disease. Women who douche regularly may do so for reasons related to their risk of acquiring a sexually transmitted infection, introducing confounding that is difficult to control in non-experimental studies. Methods. We conducted a multicenter randomized field trial with a 1-year follow-up period. The study comprised 1827 women age 18-34, with no current indication of pelvic inflammatory disease, who were regular users of a douche product and who had been treated recently for a sexually transmitted bacterial infection or bacterial vaginosis. Women were randomly assigned to use either a newly designed and marketed douche product or a soft cloth towelette, and were resupplied with product at each bimonthly follow-up visit. We measured the occurrence of pelvic inflammatory disease using a combination of clinical and laboratory indicators. We also recorded pregnancy occurrence among participants. Results. The risk of PID among women assigned to use the douche product, relative to that among women assigned to use the wipe product, was 1.05 (95% confidence interval = 0.57-1.9). Using an alternative, less sensitive definition of PID gave a risk ratio of 1.26 (0.62-2.6). The probability of becoming pregnant was 15% lower among women assigned to use a douche product, and 33% lower among women who douched more frequently (ratio = 0.67; 0.42-1.08). Conclusions. There was little or no indication of a greater risk of PID among women assigned to use the douche product. Douching may be related to a lower probability that a woman becomes pregnant