Pregnant women at risk for sPTB will be randomized to receive synbiotics or placebo from 8-10 weeks gestation until delivery. The synbiotic contains eight Lactobacillus strains, inulin, FOS, and D-mannose. Adherence will be monitored via diaries, and standard care protocols for sPTB prevention will be followed. Primary outcomes include gestational age at delivery and PTB rates, with secondary outcomes covering neonatal and microbiome analyses.