The dynamics of vaginal and rectal Lactobacillus spp. flora in subsequent trimesters of pregnancy in healthy Polish women, assessed using the Sanger sequencing method

Lactobacilli play an important role in maintaining vaginal health and protection against bacterial infections in the genital tract. The

This study showed that in the examined group of healthy, pregnant Polish women, the vaginal Lactobacillus flora, both qualitative and quantitative, was stable during the three subsequent trimesters. In contrast, the number of rectal Lactobacillus species dramatically decreased after the first trimester.

Among the patients tested, the most common species colonizing the vagina in the first trimester were: L. crispatus 29%, L. gasseri 19.4% and L. rhamnosus 16.1%, in the second trimester: L. crispatus 51.6%, L. gasseri 25.8%, L. rhamnosus 19.4% and L. amylovorus 16.1%, and in the third trimester the most common Lactobacillus species were: L. crispatus 25.8%, L. gasseri 25.8% and L. johnsonii 19.4%. In rectal species, the number decreased in the second and third trimesters in comparison to the first trimester (p = 0.003). An analysis of rectal dynamics showed that in the first trimester, the most common species were: L. johnsonii 19.4%, and L. plantarum 9.7%, in the second trimester: L. crispatus 9.7% and L. mucosae 6.5%, and in the third trimester: L. casei 9.7% and L. rhamnosus 9.7%. Individual dynamics of the Lactobacillus species composition showed variability, characterized by continuous, intermittent, or periodic colonization. The patients examined were mostly colonized by three Lactobacillus species in vagina (32.3%), whereas for the rectum, one Lactobacillus species during the whole pregnancy duration was common (32.3%).