Bacterial vaginosis (BV) in pregnancy is related to numerous adverse events; however, the validity of different methods of vaginal swab collection to diagnosis BV among pregnant women is unclear. This study examines the validity of self-collected compared with provider-collected vaginal swabs and describes the intra-rater and inter-rater reliability of BV assessment among a sample of pregnant women early in gestation. Gram-stain evaluation of vaginal samples using the Nugent criteria was conducted to determine the overall and morphotype-specific BV scores. We found strong validity for the overall and morphotype-specific scores comparing self-collected swabs to provider-collected swabs. In addition, we found excellent overall and morphotype-specific inter-rater reliability and excellent intra-rater reliability in our sample. These study results support the use of self-collected vaginal swabs for diagnosing BV and document the reliability of BV assessment among pregnant women.