Aim: This study aimed to assess amniotic fluid bacterial load using the copy number of 16S ribosomal deoxyribonucleic acid and to clarify its association with perinatal outcomes.
Methods: This retrospective diagnostic and prognostic study included 63 patients with preterm labor and suspected intra-amniotic infection who underwent amniocentesis before 34 weeks of gestation. We measured the copy number of 16S ribosomal deoxyribonucleic acid in 1 mL of amniotic fluid using droplet digital polymerase chain reaction and graded infections as Grade (G) 0, 1, 2, or 3. Case-control analysis was performed to compare G3 (N = 29), G1-2 (N = 18), and G0 (N = 17) patients. The main outcome measures were histologic chorioamnionitis, funisitis, and amniocentesis-to-delivery time windows.
Results: The frequency of histologic chorioamnionitis (Stage III) and funisitis was as follows: G3, 86% and 79%; G1-2, 28% and 56%; and G0, 0% and 6%, respectively. The rate of post-amniocentesis delivery within 1 and 2 days was as follows: G3, 62% and 83%; G1-2, 56% and 78%; G0, 13% and 25%, respectively. Comparisons between the G3 and G0 groups revealed significant differences in all criteria (p < 0.05). Additionally, significant differences were noted in pathological inflammatory findings between the G3 and G1-2 groups, as well as in all perinatal outcomes between the G1-2 and G0 groups (p < 0.05).
Conclusions: Our diagnostic method, based on the copy number of 16S ribosomal deoxyribonucleic acid, supports intra-amniotic colonization assessment, guiding clinical decisions regarding the timing of delivery and potentially informing antimicrobial interventions.
Keywords: DNA; amniotic fluid; pregnancy complications; ribosomal DNA; uterine infection.
© 2025 Japan Society of Obstetrics and Gynecology.