Objective To determine the presence and identity of extracellular bacteriophage (phage) families, genera and species in the vagina of pregnant women. Design Descriptive, observational cohort study. Setting São Paulo, Brazil. Population Pregnant women at 21–24 weeks’ gestation. Methods Vaginal samples from 107 women whose vaginal microbiome and pregnancy outcomes were previously determined were analysed for phages by metagenomic sequencing. Main outcome measures Identification of phage families, genera and species. Results Phages were detected in 96 (89.7%) of the samples. Six different phage families were identified: Siphoviridae in 69.2%, Myoviridae in 49.5%, Microviridae in 37.4%, Podoviridae in 20.6%, Herelleviridae in 10.3% and Inviridae in 1.9% of the women. Four different phage families were present in 14 women (13.1%), three families in 20 women (18.7%), two families in 31 women (29.1%) and one family in 31 women (29.1%). The most common phage species detected were Bacillus phages in 48 (43.6%), Escherichia phages in 45 (40.9%), Staphylococcus phages in 40 (36.4%), Gokushovirus in 33 (30.0%) and Lactobacillus phages in 29 (26.4%) women. In a preliminary exploratory analysis, there were no associations between a particular phage family, the number of phage families present in the vagina or any particular phage species and either gestational age at delivery or the bacterial community state type present in the vagina. Conclusions Multiple phages are present in the vagina of most mid‐trimester pregnant women. Tweetable abstract Bacteriophages are present in the vagina of most pregnant women.

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