Abstract
The vaginal microbiome plays an important role in maternal and neonatal health. Imbalances in this microbiota (dysbiosis) during pregnancy are associated with negative reproductive outcomes, such as pregnancy loss and preterm birth, but the underlying mechanisms remain poorly understood. Consequently a comprehensive understanding of the baseline microbiome in healthy pregnancy is needed. We characterized the vaginal microbiomes of healthy pregnant women at 11–16 weeks of gestational age (n = 182) and compared them to those of non-pregnant women (n = 310). Profiles were created by pyrosequencing of the cpn60 universal target region. Microbiome profiles of pregnant women clustered into six Community State Types: I, II, III, IVC, IVD and V. Overall microbiome profiles could not be distinguished based on pregnancy status. However, the vaginal microbiomes of women with healthy ongoing pregnancies had lower richness and diversity, lower prevalence of Mycoplasma and Ureaplasma and higher bacterial load when compared to non-pregnant women. Lactobacillus abundance was also greater in the microbiomes of pregnant women with Lactobacillus-dominated CSTs in comparison with non-pregnant women. This study provides further information regarding characteristics of the vaginal microbiome of low-risk pregnant women, providing a baseline for forthcoming studies investigating the diagnostic potential of the microbiome for prediction of adverse pregnancy outcomes.
Highlights
The complex microbial community present in the female lower genital tract is an important factor in a woman’s reproductive health
Vaginal microbiomes from the women who delivered infants less than 2500 g were determined to belong to Community State Types (CST) II (L. gasseri dominated) (1/3) and III (L. iners dominated) (2/3)
Vaginal microbiomes of the mothers of the five infants were determined to belong to CST III (L. iners dominated) (1/5), V (L. jensenii dominated) (2/5), IVC (G. vaginalis subgroup A dominated) (1/5) and IVD (1/5)
Summary
The complex microbial community present in the female lower genital tract is an important factor in a woman’s reproductive health. Pregnancy is associated with a variety of physiological events including increased sex steroid hormone levels[22], host immune response modulation[23, 24], altered immune-physicochemical properties of the cervical mucus[25,26,27], as well as behavioural changes such as reduced drinking and smoking[28] These factors may drive changes in the structure and/or composition of the microbial community resulting in a microbiome that is different from that of non-pregnant women. The results of these studies suggest that pregnancy has a marked effect on the vaginal microbiome, leading to greater stability, increased Lactobacillus proportional abundance and reduced richness and diversity relative to the vaginal microbiomes of non-pregnant women[29,30,31,32,33]
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