Microbiome Before Pregnancy and its Impact on Successful Conception

Written by
Fathalla Ali, Bsc MSc, MPH and PHD student UNSW

It has been assumed that the composition of microbiota of follicular fluid, semen, uterine and vagina before pregnancy contribute to a successful pregnancy (1):

  • Microbiota in the follicular fluid was found to play an important role in the pregnancy outcomes after IVF treatment. The presence of Lactobacillus spp. in the follicular fluid was associated with embryo maturation and transfer, and the protection against adverse bacteria and consequently contributed to successful IVF treatment (2).
  • Semen Health was found to be positively associated with lactobacillus dominated microbiome. This positive association was attributed to the secretion of lactic acid by lactobacillus, that maintain semen quality and centring against the negative effect of other bacteria (3).
  • A higher chance of pregnancy, ongoing pregnancy and live birth was found to be associated with lactobacillus dominated microbiota in the uterine (4).
  • Vaginal microbiota dominated by Lactobacillus before pregnancy in IVF treated women was associated with successful pregnancy (5). However, in most women, virginal microbiota is not stable and changed overtime. For example, women of European and Asian origin are more likely to have Lactobacillus dominated vaginal microbiota whereas non-pregnant Hispanic women were found to be less likely to have Lactobacillus dominated vaginal microbiota (6).


  1. Schoenmakers, S., Steegers-Theunissen, R., & Faas, M. (2019). The matter of the reproductive microbiome. Obstetric medicine12(3), 107–115. Click here
  2. Pelzer, E. S., Allan, J. A., Waterhouse, M. A., Ross, T., Beagley, K. W., & Knox, C. L. (2013). Microorganisms within human follicular fluid: effects on IVF. PloS one8(3), e59062. Click here.
  3. Weng, S. L., Chiu, C. M., Lin, F. M., Huang, W. C., Liang, C., Yang, T., Yang, T. L., Liu, C. Y., Wu, W. Y., Chang, Y. A., Chang, T. H., & Huang, H. D. (2014). Bacterial communities in semen from men of infertile couples: metagenomic sequencing reveals relationships of seminal microbiota to semen quality. PloS one9(10), e110152. Click here.
  4. Moreno, I., Codoñer, F. M., Vilella, F., Valbuena, D., Martinez-Blanch, J. F., Jimenez-Almazán, J., Alonso, R., Alamá, P., Remohí, J., Pellicer, A., Ramon, D., & Simon, C. (2016). Evidence that the endometrial microbiota has an effect on implantation success or failure. American journal of obstetrics and gynecology215(6), 684–703. Click here.
  5. Hyman, R. W., Herndon, C. N., Jiang, H., Palm, C., Fukushima, M., Bernstein, D., Vo, K. C., Zelenko, Z., Davis, R. W., & Giudice, L. C. (2012). The dynamics of the vaginal microbiome during infertility therapy with in vitro fertilization-embryo transfer. Journal of assisted reproduction and genetics29(2), 105–115. Click here
  6. Power, M. L., Quaglieri, C., & Schulkin, J. (2017). Reproductive Microbiomes: A New Thread in the Microbial Network. Reproductive sciences (Thousand Oaks, Calif.)24(11), 1482–1492. Click here