Despite advances in the control of anxiety and fear, dental treatment (DT) continues to be a stressful event, especially during pregnancy. There are several instruments to measure anxiety and fear about DT (AFDT). However, few are validated for use in Brazil. Our objective was to validate the Modified Dental Anxiety Scale (MDAS) for use in Brazil and to evaluate the association between AFDT and the use of oral health services (OHS) during pregnancy.This is a cross-sectional study nested in a prospective cohort. We conducted a face, content, and construct validation. The Visual Analogue Scale (VAS) was the comparison instrument with MDAS. Sociodemographic and behavioral characteristics were also assessed. Associations were estimated by odds ratios (OR) and 95% confidence intervals (95%CI) in multiple logistic regression analysis (alpha = 5%).There were no difficulties in the translation/back-translation process. The reproducibility of the instrument was 0.54 (P=0.01). The correlation of MDAS with VAS was 0.71 (P=0.003). The reliability of the instrument was high (Cronbach's alpha: 0.79 to 0.87). After validation, the instrument was administered to 486 women. Mild or moderate AFDT was reported by 81.3% of pregnant women and at higher levels, by 8.2%. There was no association between the use of OHS and AFDT at moderate levels (OR=2.03; 95%CI: 0.45-9.09) or high (OR=1.35; 95%CI: 0.20-9.13).MDAS is a valid instrument for measuring AFDT. The prevalence of AFDT among pregnant women is high, but this event does not seem to be associated with the use of OHS.