RESUMEN
BACKGROUND: The purpose of this study is to present the use of a non-randomized experimental design with multiple controls, with emphasis on a historical control group, as an alternative methodologic resource for studies on the association between periodontal disease and prematurity/low birth weight. METHODS: The sample consisted of 234 pregnant women: 54 in the Test Group (treatment of periodontal disease); 68 in Control Group I (without periodontal disease); and 112 in Control Group II (historical control group, with untreated periodontal disease). The diagnosis of periodontal disease was established by means of a complete clinical examination, using measurements of probing depth, gingival recession, clinical attachment loss, and bleeding index. The women in the Test Group were treated for periodontitis and followed-up with periodontal support therapy throughout their pregnancies. After delivery, they were reevaluated regarding their periodontal condition, and information on the newborn's birth weight was obtained. This was also done for Control Groups I and II. Descriptive analyses on the study variables were performed using the χ(2) and Fisher exact tests. Association measurements (relative risk) were obtained using a significance level of 5%. RESULTS: The frequency of low birth weight among the Test Group was similar to Control Group I and lower than Control Group II. CONCLUSION: The results suggest that successful periodontal therapy in pregnant women suffering from periodontitis is a protective factor promoting the birth of children with normal weight.