Microbiome in Female Reproductive Health: Implications for Fertility and Assisted Reproductive Technologies

Abstract

The microbiome plays a critical role in the process of conception and the outcomes of pregnancy. Disruptions in microbiome homeostasis in women of reproductive age can lead to various pregnancy complications, which significantly impact maternal and fetal health. Recent studies have associated the microbiome in the female reproductive tract (FRT) with assisted reproductive technology (ART) outcomes, and restoring microbiome balance has been shown to improve fertility in infertile couples. This review provides an overview of the role of the microbiome in female reproductive health, including its implications for pregnancy outcomes and ARTs. Additionally, recent advances in the use of microbial biomarkers as indicators of pregnancy disorders are summarized. A comprehensive understanding of the characteristics of the microbiome before and during pregnancy and its impact on reproductive health will greatly promote maternal and fetal health. Such knowledge can also contribute to the development of ARTs and microbiome-based interventions.

1. Introduction

With rapid social and economic development, female reproductive health has received increasing attention. There have been various proactive lifestyle recommendations to promote reproductive health, such as engaging in regular exercise and maintaining a balanced diet that includes high-fiber food [1,2]. Recent studies have indicated that the microbiome also plays a crucial role in successful pregnancy and favorable pregnancy outcomes [3,4]. Microbiome refers to the community of all commensal, symbiotic, and pathogenic microorganisms within a body or other environment, and their habitat [5]. Previous studies have shown that the microbiome plays an essential role in the healthy development of the human body and the onset of various diseases [6–8]. Microbiomes in different parts of the human body exhibit different dynamic patterns throughout different life stages, with pregnancy being one of the most critical life stages [9–12]. Previous studies focusing on mothers and babies during the perinatal period have shown frequent microbial interaction and transmission across various body sites, indicating the importance of microbial homeostasis, particularly in the gut and reproductive tract, for the health of both mothers and infants during this critical time window [9,13]. Emerging studies also suggest that the depletion of certain bacteria in early life may lead to significant health issues in childhood [14–16]. Therefore, investigating the characteristics of the microbiome before and during pregnancy, as well as understanding how the microbial variations impact pregnancy health and delivery outcomes, not only contributes to the development of risk prediction models, but also provides targets for microbiome-based interventions to improve reproductive health.

In modern times, unhealthy lifestyles have remarkably increased the incidence of pregnancy complications. These illnesses during pregnancy have a noticeable impact on healthy reproduction. Over the past few decades, the prevalence of infertility has led to the growth of assisted reproductive technologies (ARTs) [17], which provide hope to many couples facing reproductive difficulties. ART refers to any fertility-related treatment in which eggs or embryos are manipulated, with in vitro fertilization (IVF) being the main type [18]. The IVF process typically involves retrieving eggs and sperm, fertilizing the eggs, culturing and screening the embryos, and finally transferring an appropriate embryo into the uterus [18]. Recently, a lot of studies have associated the microbiome in the female reproductive tract (FRT) with ART outcomes and provided some interesting observations [19–23]. However, due to inconsistent conclusions among different studies, the progress of ARTs remains limited. A comprehensive understanding of the role of the microbiome in the ART process is crucial and urgently needed.