DNA extraction and 16S rDNA sequencing
Vaginal swab DNA was extracted using the QIAamp DNA Mini Kit (QIAGEN, Hilden, Germany) and amplified by PCR using the 16S V4 region primer 515F (5′ GTGCCAGCMGCCGCGGTAA 3′), 806R (5′ GGACTACHVGGGTWTCT AAT 3′). The PCR product was purified using GeneJET gel extraction assay (Thermo Scientific). TruSeq