Distinct vaginal microbial signatures in pregnancies complicated by antiphospholipid syndrome: depletion of <i>Lactobacillus johnsonii</i> and enrichment of <i>Bifidobacterium dentium</i>

. A logistic regression model integrating the relative abundances of these microbial biomarkers demonstrated robust diagnostic performance in differentiating pregnancies with APS from healthy pregnancies, with risk scores significantly correlating with clinical parameters and pregnancy outcomes. This study demonstrates that pregnant women with APS display a distinct vaginal microbiome pattern defined by species-specific compositional restructuring rather than global dysbiosis. These microbial alterations may contribute to APS-related pregnancy morbidity, highlighting vaginal microbial signatures as promising noninvasive biomarkers for risk stratification and potential therapeutic targets in obstetric APS management. IMPORTANCE: , a bacterium typically found in the gut. Unlike typical vaginal infections that display widespread microbial dysbiosis, antiphospholipid syndrome induces only selective alterations in specific bacterial species. These microbial signatures correlated with hematological parameters and adverse pregnancy histories, including prior miscarriages. Our findings suggest that monitoring vaginal microbiota could provide a simple, noninvasive approach to identify high-risk pregnancies in women with antiphospholipid syndrome and may guide novel screening strategies for pregnancy-related disorders targeting the vaginal microbiome.