The maternal microbiome is recognized as a key determinant of a range of important maternal and child health outcomes, and together with perinatal factors influences the infant microbiome. This manuscript provides a summary review of research investigating: (1) the role of the maternal microbiome in pregnancy outcomes known to adversely influence neonatal and infant health, including preterm birth, cardiometabolic complications of pregnancy such as preeclampsia and gestational diabetes, and excessive gestational weight gain; (2) factors with an established link to adverse pregnancy outcomes that are known to influence the composition of the maternal microbiome; and (3) strategies for promoting a healthy maternal microbiome, recognizing that much more research is needed in this area.

Introduction Perineal lacerations during childbirth affect more than 65% of women in the United States. Little attention has been given to the long-term biologic consequences associated with perineal lacerations or possible associations with postpartum mental health. In this article we describe the results of a study that explored inflammatory pathways in women who reported perineal lacerations during childbirth and the relationship with stress and depressive symptoms during the first six months postpartum. Methods A repeated measures design was used to explore the relationship between varying degrees of perineal lacerations, inflammatory cytokines, postpartum stress, and depressive symptoms in 153 women over six months. Depressive symptoms were measured using the Edinburg Postnatal Depression Scale (EPDS) and maternal stress via the Perceived Stress Scale (PSS). Plasma was analyzed for pro (TNF-α, IL-6, IL-1β, IFN-γ) and anti-inflammatory (IL-10) cytokines. Levels of cytokines were compared between women with or without varying degrees of injury. Results A relationship was identified between symptoms of depression and a 2nd degree or more severe perineal laceration starting at 1 month postpartum (P=0.04) and continuing through 3 months (P=0.03). Similarly, stress symptoms were higher at 3 months postpartum (P=0.02). Markers of inflammation were significantly higher among this group with IL-6 increased at 2 weeks postpartum (P=0.02), and remaining elevated through 2 months postpartum (P=0.003); there were also significant differences in pro to anti-inflammatory cytokine ratios out to 6 months postpartum. Regression analysis indicated that 2nd degree or more severe lacerations accounted for 5.9% of the variance in EPDS score at one month postpartum (P=0.024, F=2.865, t=2.127), increasing substantially when the 1-month stress score was included as well. Discussion This study suggests that perineal lacerations, inflammation, stress, and depressed mood are associated, however, more research is needed to elucidate the actual relationship between inflammation and mental health in women who experience such injuries.

The human microbiome plays a role in maintaining health, but is also thought to attenuate and/or exacerbate risk factors for adverse maternal-child health outcomes. The development of the microbiome begins in utero, however factors related to the labor and birth environment have been shown to influence the initial colonization process of the newborn microbiome. This “seeding” or transfer of microbes from the mother to newborn may serve as an early inoculation process with implications for the long-term health outcomes of newborns. Studies have shown that there are distinct differences in the microbiome profiles of newborns born vaginally compared to those born by cesarean. Antibiotic exposure has been shown to alter the microbial profiles of women and may influence the gut microbial profiles of their newborns. Considering that the first major microbial colonization occurs at birth, it is essential that labor and birth nurses be aware of factors that may alter the composition of the microbiome during the labor and birth process. The implications of various activities and factors unique to the labor and birth environment that may influence the microbiome of women and newborns during the labor and birth process (e.g. route of birth, antibiotic use, nursing procedures) are presented with a focus on the role of labor nurses and the potential influence of nursing activities on this process.

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Preterm Birth (PTB, < 37 completed weeks' gestation) is one of the leading obstetrical problems in the United States affecting approximately 1 of every 9 births. Even more concerning are the persistent racial disparities in PTB with particularly high rates in African Americans. There are several recognized pathophysiologic pathways to PTB, including infection and/or exaggerated systemic or local inflammation. Intrauterine infection is a causal factor linked to PTB, thought to result most commonly from inflammatory processes triggered by microbial invasion of bacteria ascending from the vaginal microbiome. Trials to treat various infections have shown limited efficacy in reducing PTB risk, suggesting that other complex mechanisms, including those associated with inflammation, may be involved in the relationship between microbes, infection, and PTB. A key mediator of the inflammatory response, and recently shown to be associated with PTB, is the complement system, an innate defense mechanism involved in both normal physiologic processes that occur during pregnancy implantation, as well as processes that promote the elimination of pathogenic microbes. The purpose of this paper is to present a mechanistic model of inflammation-associated PTB, which hypothesizes a relationship between the microbiome and dysregulation of the complement system. Exploring the relationships between the microbial environment and complement biomarkers may elucidate a potentially modifiable biological pathway to preterm birth.