Background: During pregnancy many physiological, anatomical and biochemical changes take place that affect almost all body systems. In the oral pregnant women have serious changes such as more sever dental caries. This study was conducted to measure dental caries severity and selected salivary variables (salivary flow rate, PH and viscosity)and to find the relation of dental caries with these salivary variables. Subjects, materials and methods: The study group consisted of 60 pregnant women that were divided into three equal groups according to trimester (20 pregnant women in each trimester).They were selected randomly from the Maternal and Child Health Care Centers in Baghdad city, the age range was 20-25 years. In addition to 20 unmarried women as a control group and matched with age. Stimulated salivary samples were collected .Then salivary flow rate, pH and viscosity were measured. Dental caries severity was recorded by using Decay, Missing and Filled index (D1-4MFS) using the criteria described by Manjie et al, (1989). Plaque index system by Silness and Löe, (1964) was used for measuring dental plaque thickness. For measuring dental calculus the calculus index component of the periodontal diseases index (PDI) by Ramfjord (1959) was used. Results: Results of the current study revealed that dental caries parameter represented by (DMFT ,DMFS,DS and MS) were higher among pregnant than non –pregnant women with significant differences (p<0.05) for DMFT,DMFS and DS also all grades of lesion severity(D1-4)were higher among pregnant than non –pregnant women with nonsignificant differences(p>0.05).Almost all dental caries parameter were higher in the 2nd trimesters with highly significant difference (p<0.01) for D1,DS ,DMFS and DMFT among four groups . Concerning oral cleanliness both plaque and calculus indices recorded higher values among pregnant than non-pregnant with highly significant difference for both (p<0.01). Values were higher during 2nd trimester with high significant and non-significant differences among four groups .Regarding the relations of dental caries with oral cleanliness ,it was found that all dental caries parameters recorded positive correlations with both plaque and calculus indices with significant and highly significant relations Regarding salivary variables ,results revealed that salivary flow rate was higher among pregnant (especially in the 2nd trimester)than non-pregnant women but with non-significant difference (p>0.05).On the other hand salivary PH value was lower among pregnant than non-pregnant women with highly significant difference (p<0.01)among them. Salivary PH was lowest in the 2nd trimester with highly significant difference (p<0.01) among four groups .Also Salivary viscosity was higher among pregnant than non-pregnant women with highly significant difference (p<0.01) and it recorded higher mean value in the 3rd trimester with highly significant difference among four groups (p<0.01). Salivary PH recorded inverse relation with almost all dental caries parameters with significant relations with D4, MS and highly significant relations with DS,DMFS and DMFT ,while salivary flow rate and salivary viscosity revealed non-significant relations with dental caries parameters (p>0.05). Conclusion: Dental caries severity was higher among pregnant women probably due to the effect of pregnancy itself on oral hygiene (higher plaque and calculus indices) and salivary variables (increased salivary acidity and viscosity).Therefore, intensive education and preventive programs should be directed for pregnant women.