The genital tract microbiota of IVF patients and oocyte donors: a comparative analysis

Recent studies have observed an association between genital tract microbiota and reproductive outcomes in patients undergoing in vitro fertilization (IVF). This finding could be caused by ascending dysbiosis from the vagina to the endometrium. The main objective of this study was to compare the microbiota and total bacterial load in the vagina, cervix and endometrium of IVF patients and oocyte donors. Thus, a total of two cohorts were explored: IVF patients (N=27) and healthy oocyte donors (N=26). The microbiota was investigated using 16S rRNA gene sequencing of the V3-V4 hypervariable regions, as well as qPCR for common vaginal species and total bacterial load. The study used a transcervical sampling approach for the endometrial microbiota samples. The highest bacterial load was seen in the vagina (median 2.6*109; 95% CI 9.7*108 - 7.1*109; 16S rRNA gene copies/swab), followed by the cervix (median 9.0*107; 95% CI 3.3*107 - 2.4*108; 16S rRNA gene copies/swab) and the endometrium (median 8.6*106; 95%CI 3.1*106 - 2.4*107; 16S rRNA gene copies/swab). Only 1% of the observed variation between genital tract samples was explained by patient group (IVF patient or oocyte donor) and less than 1% of the variation between genital tract samples was explained by the anatomical site. Although, findings could be impacted by the transcervical sampling approach, 16S rRNA gene sequencing as well as species-specific qPCR showed a similar microbiota composition present in the cervix and the endometrium when compared to the vaginal microbiota.