Vaginal microbiota alterations under supraphysiological estradiol state during in vitro fertilization-embryo transfer (IVF-ET) and the association with reproductive outcomesOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This prospective study asked how the high-estradiol state created by in vitro fertilization-embryo transfer (IVF-ET) reshapes the vaginal microbiome and whether those changes affect pregnancy outcomes. Vaginal swabs were collected before embryo transfer and profiled by 16S rRNA sequencing. Women were grouped by peak estradiol or endometrial preparation, and microbes were linked to reproductive outcomes using LEfSe, correlation, and ROC analysis.
Who was studied?
The cohort was 92 Chinese infertile women, aged 22 to 40, treated at a Hangzhou reproductive center from April 2023 to March 2024. Fresh transfer patients were split into high (n=25), median (n=26), and low estradiol (n=16) groups. Frozen transfer patients formed natural cycle (n=15) and hormone replacement (n=10) groups. All had two high-grade cleavage embryos transferred.
What were the most important findings?
Higher estradiol lowered vaginal diversity and pushed communities toward Lactobacillus dominance. Lactobacillus averaged 68.93 percent in the high-estradiol group versus 53.04 percent in the low-estradiol group. Streptococcus_anginosus and Akkermansia rose with estradiol, while Escherichia-Shigella fell. Ongoing pregnancy did not improve with Lactobacillus dominance and was highest in the natural cycle group (93.3 percent). Streptococcus, Atopobium, and Bifidobacterium predicted adverse outcomes, with ROC AUC values of 0.758, 0.899, and 0.876.
What are the greatest implications of this study?
The results indicate that a Lactobacillus-dominant vaginal microbiome under supraphysiological estradiol does not translate into better IVF success. Streptococcus, which rose with estradiol and marked non-pregnancy, may act as a microbial mediator impairing reproduction under high-estrogen conditions. Because the sample was small and cross-sectional in design, these associations need confirmation in larger prospective studies before they guide clinical decisions.