Surreal illustration of pregnant woman with glowing bacteria representing vaginal microbiome.

Decoding the Vaginal Microbiome: How Pregnancy Changes the Landscape

Kai Mendoza in Health & Wellness November 2025 • 4 min read.

"A closer look at how pregnancy impacts vaginal health and why understanding these changes is key to preventing complications."

The vaginal microbiome, a complex community of microorganisms, plays a pivotal role in women's health, especially during pregnancy. When this delicate balance is disrupted (a state known as dysbiosis), it can lead to adverse outcomes such as pregnancy loss and preterm birth. To better understand and prevent these complications, scientists are diving deep into the specifics of how pregnancy alters this microbial landscape.

A groundbreaking study compared the vaginal microbiomes of pregnant and non-pregnant women, revealing significant differences in richness, diversity, and the presence of specific bacterial groups. This research provides a crucial baseline for future studies aiming to predict and prevent adverse pregnancy outcomes by harnessing the power of microbiome diagnostics.

By characterizing the vaginal microbiomes of healthy pregnant women and comparing them to those of their non-pregnant counterparts, researchers are paving the way for more effective strategies to safeguard maternal and neonatal health.

Key Shifts in the Vaginal Microbiome During Pregnancy

Surreal illustration of pregnant woman with glowing bacteria representing vaginal microbiome.

The study, published in Scientific Reports, analyzed vaginal microbiome samples from 182 pregnant women (11-16 weeks gestation) and 310 non-pregnant women. Using pyrosequencing of the cpn60 universal target region, researchers identified distinct Community State Types (CSTs) within these microbiomes. While the overall CST distribution didn't differ dramatically based on pregnancy status, deeper analysis revealed notable changes.

Here are some of the key findings:

Reduced Richness and Diversity: Pregnant women exhibited lower microbial richness and diversity compared to non-pregnant women.
Lower Prevalence of Mollicutes: The presence of Mycoplasma and Ureaplasma was significantly reduced in pregnant women.
Increased Lactobacillus Abundance: Pregnant women, particularly those with Lactobacillus-dominated CSTs, showed a greater abundance of these beneficial bacteria.
Higher Bacterial Load: Overall, pregnant women had a higher total bacterial load in their vaginal microbiomes.

These shifts suggest that pregnancy promotes a less diverse but more stable vaginal environment, potentially dominated by Lactobacillus species. This dominance is thought to contribute to a protective effect, maintaining a low vaginal pH that inhibits the growth of harmful bacteria.

The Road Ahead: Using Microbiome Insights for Better Prenatal Care

This study adds valuable insights into the vaginal microbiome during pregnancy, providing a foundation for future research exploring the diagnostic potential of the microbiome in predicting adverse pregnancy outcomes. By understanding the nuances of these microbial shifts, we can work towards developing targeted interventions to promote healthier pregnancies and reduce the risk of complications for both mother and child.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1038/s41598-017-07790-9, Alternate LINK

Title: The Vaginal Microbiome Of Pregnant Women Is Less Rich And Diverse, With Lower Prevalence Of Mollicutes, Compared To Non-Pregnant Women

Subject: Multidisciplinary

Journal: Scientific Reports

Publisher: Springer Science and Business Media LLC

Authors: Aline C. Freitas, Bonnie Chaban, Alan Bocking, Maria Rocco, Siwen Yang, Janet E. Hill, Deborah M. Money

Published: 2017-08-23

Everything You Need To Know

What is the significance of the vaginal microbiome, especially during pregnancy, and what happens when its balance is disrupted?

The vaginal microbiome is a complex community of microorganisms that resides in the vagina. It plays a crucial role in women's health, particularly during pregnancy. When the balance of this community is disrupted, a state known as dysbiosis, it can lead to adverse outcomes such as pregnancy loss and preterm birth. Maintaining a healthy vaginal microbiome is essential for preventing these complications.

How does pregnancy alter the composition of the vaginal microbiome, and what are the key shifts observed?

During pregnancy, the vaginal microbiome undergoes several key shifts. These include reduced microbial richness and diversity, a lower prevalence of Mollicutes like Mycoplasma and Ureaplasma, an increased abundance of Lactobacillus species, and a higher overall bacterial load. These changes suggest that pregnancy promotes a less diverse but more stable vaginal environment, potentially dominated by Lactobacillus.

What are Community State Types (CSTs) in the context of the vaginal microbiome, and how are they relevant to understanding pregnancy-related changes?

Community State Types, or CSTs, are distinct classifications of vaginal microbiomes based on the dominant bacterial species. While the overall distribution of CSTs didn't dramatically differ between pregnant and non-pregnant women, deeper analysis revealed notable changes in bacterial abundance. Understanding CSTs helps researchers characterize and compare the vaginal microbiomes of different individuals or groups.

Why is there an increased abundance of Lactobacillus during pregnancy in the vaginal microbiome, and what protective benefits does this dominance provide?

The increased abundance of Lactobacillus species during pregnancy is thought to be beneficial because Lactobacillus helps maintain a low vaginal pH. This acidic environment inhibits the growth of harmful bacteria, providing a protective effect against infections and other adverse outcomes. However, it's crucial to note that while Lactobacillus dominance is generally considered beneficial, an overabundance or lack of diversity within Lactobacillus species might also have implications that require further investigation.

How can the insights from studying the vaginal microbiome be used to improve prenatal care and predict adverse pregnancy outcomes?

The insights gained from studying the vaginal microbiome during pregnancy can potentially revolutionize prenatal care by allowing for the development of microbiome diagnostics to predict adverse pregnancy outcomes. By understanding the nuances of microbial shifts, targeted interventions can be developed to promote healthier pregnancies and reduce the risk of complications for both mother and child. Future research could explore personalized interventions based on an individual's microbiome profile.