How does an altered genital tract microbiome contribute to PTB?

• A. It enhances immunity
• B. It decreases uterine contractions
• C. It induces inflammatory responses
• D. It promotes fetal growth

Answer: (C)

An altered genital tract microbiome can significantly contribute to preterm birth (PTB) primarily through its ability to induce inflammatory responses. When the balance of the microbiome is disrupted, pathogenic bacteria may overgrow, leading to an imbalance that triggers an inflammatory response. This inflammation can affect the uterine environment, promoting the release of pro-inflammatory cytokines and other mediators. These inflammatory signals can lead to premature activation of labor, which is a key factor in PTB.

In contrast, the other choices do not align with how an altered microbiome contributes to PTB. While a healthy microbiome can enhance immunity, an altered one typically disrupts it, leaving the body more susceptible to infections that can lead to PTB. The decreased uterine contractions would suggest a mechanism that prevents PTB, rather than contributes to it. Finally, promoting fetal growth isn't a typical consequence of an altered microbiome; instead, such alterations are more likely to impair gestational development due to the associated inflammatory processes. Thus, the induction of inflammatory responses is the most relevant mechanism linking an altered microbiome to preterm birth.