Abstract
Pregnancy permanently alters maternal anatomy, physiology and immunity. We evaluated if the vaginal microbiome differed between women with a first or subsequent conception. Relative abundance of bacteria in the vaginal microbiome in first trimester pregnant women, 52 with their first known conception, 26 with a prior spontaneous or induced abortion but no deliveries and 77 with at least one prior birth, was determined by classifying DNA sequences from the V1-V3 region of bacterial 16 S rRNA genes. Lactobacillus crispatus was the numerically most abundant bacterium in 76.4% of women with a first conception, 50.0% with only a prior spontaneous or scheduled abortion and 22.2% with a prior birth (p ≤ 0.01). L. iners was the most abundant bacterium in 3.8% of women with a first conception as compared to 19.2% (p = 0.03) and 20.8% (p = 0.03) in those with a prior abortion or birth, respectively. Gardnerella as the most abundant bacterial genus increased from 3.8% in women with a first conception to 15.4% and 14.3% in those with a prior abortion or birth, respectively (p > 0.05). L. iners dominance was also associated with a history of spontaneous abortion (p ≤ 0.02). The composition of the vaginal microbiome and its influence on pregnancy outcome varies with pregnancy history.
Highlights
The influence of the vaginal microbiome on pregnancy outcome remains unsettled
There was a marked decrease in the relative abundance of L. crispatus and a concomitant increase in the relative abundance of other Lactobacillus species as well as Gardnerella in women with a prior conception, regardless of whether or not this proceeded to a birth
It appears that alterations in the vaginal microenvironment in women with a prior conception or delivery favor the proliferation of Gardnerella, L. iners and L. gasseri at the expense of L. crispatus
Summary
The influence of the vaginal microbiome on pregnancy outcome remains unsettled. It has been reported that the vaginal microbiota differs[5] or does not differ[6] between women who deliver prematurely or at term. The influence of a prior conception on the composition of the vaginal microbiota during gestation has not previously been investigated. In the present study we evaluated whether the vaginal microbiota in first trimester pregnant women varied depending on whether or not this was their first conception or first delivery. This time period was studied because successful implantation of the embryo into the uterine wall and initiation of vascular changes leading to development of the placenta during the first trimester may be the stages most susceptible to pregnancy disruption[7]
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