Fig. 1.

The comparison of 16S rRNA gene copy number among various sample types. a Standard curves for tenfold diluting series (10⁷ copies to 10 copies) of Escherichia coli 16S ribosomal DNA. b Comparison of 16S rRNA gene copy numbers among various sample types. Statistical significance was assessed by the Mann–Whitney U test.  Sec AF in cohort 1, second trimester amniotic fluid in cohort 1; Del AF, delivery amniotic fluid in cohort 1; Sec AF in cohort 2, second trimester amniotic fluid in cohort 2; SC, sampling controls; EC, extraction controls; AC, amplification controls; VS, vaginal swab