Alterations of the human microbiome are a known characteristic of various inflammatory disease states and have been linked to spontaneous preterm birth and other adverse pregnancy outcomes. Recent advances in metagenomic research have proven that the placenta harbors its own rich diverse microbiome, even in clinically healthy pregnancies, and preterm birth may be a result of hematogenous infection rather than exclusively ascending infection as previously hypothesized. In this review, we describe the microbiome in healthy nongravid and gravid women to contrast it with the alterations of the microbiome associated with spontaneous preterm birth. We also discuss the importance of host gene-environment interactions and the potential for microbiota-specific targeted therapies to reduce the risk of adverse pregnancy outcomes.
Objective
To identify characteristics that predict resolution of placenta previa and to develop a clinical model for likelihood of resolution.
Methods
We conducted a retrospective study of 366 singleton pregnancies complicated by placenta previa diagnosed with resolution of the previa as the primary outcome. Regression analyses were performed to determine variables associated with resolution, and optimal timing for repeat sonographic evaluation. A likelihood of resolution model was created using a parametric survival model with Weibull hazard function.
Results
Of the 366 cases, 84% of complete placenta previas and 98% of marginal placenta previas resolved at a mean gestational age of 28.6 ±5.3 weeks. Only gestational age and distance from the internal cervical os at the time of diagnosis were significantly associated with resolution (p<0.01). Likelihood of resolution was not significantly associated with any other variables.
Conclusion
Only gestational age and distance from the internal os at time of diagnosis predict likelihood of resolution of placenta previa. Marginal previas diagnosed in the 2nd trimester do not appear to warrant repeat ultrasound evaluation for resolution.
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