The aim of the present study was to compare negative impacts of oral conditions in Oral Heath Related Quality of Life (OHRQoL) assessed by the Oral Health Impact Profile-14 (OHIP-14) scores in pregnant women receiving or not comprehensive periodontal treatment. This randomized controlled clinical trial included pregnant women aged between 18 and 35 years old. Participants were randomized in a test group with 96 and a control group with 114 women. Patients in the test group received comprehensive periodontal treatment, supra and subgingival scaling and root-planning and periodontal maintenance appointments. The OHIP-14 was applied before and after treatment. The primary outcome was changes in OHIP-14 scores after follow-up period. The impact of having received or not comprehensive periodontal treatment on the change of the OHIP-14 scores was also investigated. Both groups showed significant reduction in OHIP-14 scores and effect size for the test group was 0.60 and 0.36 for the control group. Multinomial logistic regression analysis showed that participants of the control group had 5.9-fold odds (CI 95% 1.88-18.52) of worsening in OHIP-14 scores and their perception of oral conditions in relation to test group. Comprehensive periodontal treatment during pregnancy can reduce the negative impacts in OHRQoL.