BACKGROUND: Accurate prediction of spontaneous preterm labor/preterm birth in asymptomatic women remains an elusive clinical challenge because of the multi-etiological nature of preterm birth. OBJECTIVE: The aim of this study was to develop and validate an immunoassay-based, multi-biomarker test to predict spontaneous preterm birth. MATERIALS AND METHODS: This was an observational cohort study of women delivering from December 2017 to February 2019 at 2 maternity hospitals in Melbourne, Australia. Cervicovaginal fluid samples were collected from asymptomatic women at gestational week 16 þ0 À24 þ0 , and biomarker concentrations were quantified by enzymelinked immunosorbent assay. Women were assigned to a training cohort (n ¼ 136) and a validation cohort (n ¼ 150) based on chronological delivery dates. RESULTS: Seven candidate biomarkers representing key pathways in utero-cervical remodeling were discovered by high-throughput bioinformatic search, and their significance in both in vivo and in vitro studies was assessed. Using a combination of the biomarkers for the first 136 women allocated to the training cohort, we developed an algorithm to stratify term birth (n ¼ 124) and spontaneous preterm birth (n ¼ 12) samples with a sensitivity of 100% (95% confidence interval, 76À100%) and a specificity of 74% (95% confidence interval, 66À81%). The algorithm was further validated in a subsequent cohort of 150 women (n ¼ 139 term birth and n ¼ 11 preterm birth), achieving a sensitivity of 91% (95% confidence interval, 62À100%) and a specificity of 78% (95% confidence interval, 70À84%). CONCLUSION: We have identified a panel of biomarkers that yield clinically useful diagnostic values when combined in a multiplex algorithm. The early identification of asymptomatic women at risk for preterm birth would allow women to be triaged to specialist clinics for further assessment and appropriate preventive treatment.