There have been a number of studies that discuss the importance of the microbiome transfer between mother and child; however few studies have looked into the changes that occur to the mother's vaginal microbiome during pregnancy.
A new paper published in the journal Microbiome by AMI Scientific Advisory Board member Dr. Jacques Ravel of the University of Maryland School of Medicine presents a longitudinal study of the vaginal microbiome of women during the course of pregnancy and compared that with women who were not pregnant. The overall findings of the study conclude that there are statistically significant differences in the vaginal bacterial populations between pregnant and non-pregnant women. Furthermore, the microbiome of pregnant women was more stable in non-pregnant women.
While there is a difference in the microbiome between pregnant and non-pregnant women, the authors stress that this difference in microbiomes may NOT be exclusive to pregnancy; therefore at this point, not suitable for diagnostic purposes (say determining pregancy). Furthermore, it is not known if these differences in any way benefit pregnant women or are just the result of different vaginal environments, for example higher estrogen levels in the vagina.
Finally, another paper that was possibly from the same longitudinal study showed no statistical connection between the vaginal microbiomes of women who go into pre-term labor and those who carry their child full term.