An abnormal vaginal microbiota composition has been shown to lead to pre-term births, miscarriage, and problems with conceiving. Studies have suggested that dysbiosis reduces successful early pregnancy development during IVF. However, conflicting reports exist. This meta-analysis aims to answer the following question: what is the aggregated effect found by studies investigating the influence of the vaginal microbiota composition on early pregnancy rates after IVF treatment?

A systematic review was performed using the Medline and EMBASE databases, using search terms for healthy vaginal microbiota, abnormal vaginal microbiota, fertility and pregnancy. The search resulted in six included articles. Of these, all six were used for further meta-analysis. The main outcome measures were the clinical pregnancy rate, determined through ultrasound proven fetal heartbeat and/or hCG results before 10 weeks gestation, in relation to the vaginal microbiota composition.

We found a correlation between abnormal vaginal microbiota and lower rates of early pregnancy development after IVF treatment (OR = 0.70, 95% CI = 0.49 - 0.99). One study showed the reverse correlation. However, heterogeneity between study methodologies in various forms was found.

In conclusion, women with an abnormal vaginal microbiota are roughly 1.4 times less likely to have a successful early pregnancy development after IVF treatment when compared to women with normal microbiota.