Associations between vaginal flora, MIP-1α, IL-17A, and clinical pregnancy rate in AIH

Problem: To investigate how asymptomatic bacterial imbalance affects the clinical pregnancy rate after artificial insemination with the husband's semen (AIH).

Methods: This study included married heterosexual couples who underwent AIH. According to the follow-up results, participants were divided into the pregnancy and non-pregnancy groups. Based on the first 10 pair participants in each group with vaginal flora bacterial 16S rRNA sequencing results, six semen samples received bacterial-sperm mixed test. Moreover, 34 cytokines were detected in the peripheral blood sera of the first three pairs by high-throughput Luminex, which were verified in vaginal secretions, cervical mucus, and blood sera from the first 200 pairs by ELISA.

Results: The results of the 16S sequencing of vaginal secretions showed that compared with the pregnant group, the non-pregnant group had a significantly increased bacterial species diversity, which was mainly manifested by a decrease in Lactobacillus crispatus and an increase in Prevotella bivia. When Prevotella bivia or Lactobacillus crispatus were mixed with sperms, the sperm motility was decreased (p < .05). The vaginal posterior fornix secretions, cervical mucus, and peripheral blood sera of the non-pregnant group showed decreased levels of MIP-1α and increased levels of IL-17A (p < .05).

Conclusion: The imbalance of vaginal flora leading to the increase of Prevotella bivia and the decrease of Lactobacillus crispatus may cause an imbalance of immune regulation. Low expression of MIP-1α and high expression of IL-17A were associated with reduced clinical pregnancy rate in AIH.