Table 1 Overview of placental microbiota studies that were based on 16S rRNA gene sequencing data and that were included in this critical review and re-analysis. The presented study characteristics include the: name of the first author(s); geographical location at which subjects were sampled; specific 16S rRNA gene hypervariable region that was targeted for sequencing; number of placentas sampled by mode of delivery and whether delivery was before (i.e., preterm) or after (i.e. term) 37 weeks; number of technical controls included to address potential background DNA contamination; and whether we were able to categorize placental samples based on mode of delivery, gestational age at delivery (i.e., before or after 37 weeks), and whether DECONTAM analysis could be performed to identify background DNA contaminants (i.e., N ≥ 6 technical controls included in the study) [97]. Square brackets indicate that available sample metadata did not allow for placentas to be grouped by gestational age at delivery.

From: Is there a placental microbiota? A critical review and re-analysis of published placental microbiota datasets