a, b, The association of vaginal lactobacilli with the mode of delivery, as determined by the analysis of 466 samples by 16S amplicon sequencing that were successfully sequenced twice using the Mpbio (a) and Qiagen (b) DNA isolation methods. Comparisons of the Mpbio and Qiagen DNA isolation techniques highlight that the same patterns are observed in the associations with mode of delivery. Comparisons also show that the Qiagen DNA isolation was more sensitive, resulting in twice as many signals above the 1% threshold. c–h, The association of bacterial groups with mode of delivery. Analyses were performed using all 498 placental samples with the highest value of either DNA isolation method for each bacterial group per sample. c, d, S. agalactiae was not associated with the mode of delivery irrespective of whether a 1% threshold was used (the minimum percentage considered to be potentially ecologically relevant) (c) or a 0.1% threshold was used (the 16S detection limit, relevant for detecting traces of contamination during delivery) (d). e, f, The Ureaplasma genus was significantly associated with the mode of delivery using the 0.1% threshold, similar to Fig. 2c, which describes the combination of all vaginosis-associated bacteria. g, h, F. nucleatum was not associated with the mode of delivery, irrespective of whether a 1% (g) or 0.1% (h) threshold was used. *P < 0.05, **P < 0.01, ***P < 0.001, Mann–Whitney U-tests. Source data