Pregnancy-Related Ecological Shifts of Salivary Microbiota and its Association with Salivary Sex Hormones

Abstract Background: The interactions between hosts, oral microbiomes and microenvironments have been the subject of much research in recent years. Yet, whether the alterations in the host impact the oral microbiome is not understood well. The fluctuation of sex hormone levels during pregnancy is a dramatic change in the host, and is closely related to pregnancy-associated gingivitis. In this study, salivary estradiol and progesterone level were measured at three trimesters of pregnancy and after delivery (t1: ≤ 14weeks；t2: 20–25 weeks；t3: 33–37 weeks; t4: 42 days after delivery) from 11 pregnant and 7 non-pregnant volunteers, and their salivary microbiome were collected and profiled by 16S rDNA gene sequencing. Results: The diversity of the salivary microbiome increased significantly in t3, compared to the t1 ( P <0.05), and a close parallel to the shift is found in the elevation of salivary sex hormones. Addionally, Capnocytophaga gingivalis, Peptoniphilus sp.oral taxon 386, Prevotella baroniae, Simonsiella muelleri and Lactobacillus reuteri were correlated to the fluctuation of sex hormone levels. Conclusions: The diversity of the salivary microbiome in pregnant women was elevated with the gestation weeks, which was found parallel to the changes in estradiol and progesterone levels in saliva. Rather than highly abundant bacteria, the low abundant bacteria were more vulnerable to the host impact.