Intrauterine devices and pelvic inflammatory disease: Meta-analyses of published studies, 1974-1990

We conducted a meta analysis of 36 papers published between 1974 and 1990 t o estimate the effects of intrauterine device (IUD) use and Dalkon Shield u se, in particular; on pelvic inflammatory disease (PID). The number of wome n studied in each report ranged from SD to 26,507. For general IUD use, ana lyses were separated by type of PID (symptomatic or asymptomatic) because o f extreme rate-ratio heterogeneity across studies. Dalkon Shield rate ratio s were more homogeneous and were considered in a single mete-regression. we re was substantial heterogeneity, however, in all three mete-regressions; t he rate-ratio estimates ranged from 0.51 to 12 for IUD use and symptomatic PID, from 1.0 to 132 for IUD use and asymptomatic PID, and from 0.32 to 28 for Dalkon-Shield use and FID. This heterogeneity appeared to be due to dif ferences in reference groups, study populations, and characteristics of stu dy design. We observed consistent, positive associations of IUD use with bo th symptomatic and asymptomatic PID. These associations were largest for th e Dalkon Shield.