Cohort Profile: Investigation into Biomarkers to Predict Preterm Birth (INSIGHT) -- a Prospective Pregnancy Cohort Focused on Preterm Birth in the United Kingdom

1. PurposeSpontaneous preterm birth (sPTB), particularly early preterm birth and mid-trimester loss, remains poorly understood and difficult to predict. The INSIGHT cohort was established to create a deeply phenotyped, longitudinal pregnancy dataset integrating clinical data and biological sampling to investigate the mechanisms of cervical shortening and sPTB, with a focus on linking innate immune responses, the vaginal microbiome, and host biology to identify early biomarkers of risk. 2. Participants2272 pregnant women (8+0 -28+0 weeks gestation) were enrolled as high or low risk of preterm birth based on obstetric history, cervical length, cervical procedures, multiple pregnancy, or Mullerian anomalies. Serial clinical data and biological samples, including cervicovaginal specimens and blood, were collected throughout pregnancy. 3. Findings to dateThe cohort has generated comprehensive multi-omic data, including transcriptomic, microbiome, metabolomic, proteomic, and immune profiling. Key findings demonstrate that maternal plasma cfRNA can predict early sPTB months before clinical presentation, and that integration of cervicovaginal microbiota, metabolites, and host immune markers improves risk prediction and provides mechanistic insight into inflammatory pathways leading to sPTB. 4. Future plansRecruitment concluded in 2023, with final visits occurring in 2024. Ongoing analyses focus on refining predictive models, defining biological subtypes of preterm birth, and translating integrated biomarker panels into clinically scalable risk stratification tools. STRENGTHS AND LIMITATIONS OF THIS STUDYO_LILarge, prospective longitudinal cohort (Strength): Ten years of recruitment with repeat sampling enabled detailed study of biological pathways leading to sPTB. C_LIO_LIBroad risk spectrum with clear definitions (Strength): Inclusion of both high and low-risk women using pre-specified clinical criteria supported robust comparative analyses and biomarker discovery. C_LIO_LIMulticentre NHS recruitment (Strength): Inclusion of several sites, particularly the diverse Lambeth population at St Thomas, enhanced population diversity and external validity. C_LIO_LIHospital-based, high-risk enrichment (Limitation/Strength): Recruitment from specialist preterm birth clinics and secondary/tertiary care may limit generalisability to lower-risk or primary care populations. However, it did ensure many preterm birth events were captured prospectively in this study. C_LIO_LIIncomplete follow-up and limited late sampling (Limitation): Attrition and sampling only up to a prespecified gestation (defined by standard clinical pathway) reduced full pregnancy coverage of longitudinal data. C_LI