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IntroductionMaternal sepsis remains a leading cause of death in pregnancy. Physiological adaptations to pregnancy obscure early signs of sepsis and can result in delays in recognition and treatment. Identifying biomarkers that can reliably diagnose sepsis will reduce morbidity and mortality and antibiotic overuse. We have previously identified an immune-metabolic biomarker network comprising three pathways with a >99% accuracy for detecting bacterial neonatal sepsis. In this prospective study, we will describe physiological parameters and novel biomarkers in two cohorts—healthy pregnant women and pregnant women with suspected sepsis—with the aim of mapping pathophysiological drivers and evaluating predictive biomarkers for diagnosing maternal sepsis.Methods and analysisWomen aged over 18 with an ultrasound-confirmed pregnancy will be recruited to a pilot and two main study cohorts. The pilot will involve blood sample collection from 30 pregnant women undergoing an elective caesarean section. Cohort A will follow 100 healthy pregnant women throughout their pregnancy journey, with collection of blood samples from participants at routine time points in their pregnancy: week 12 ‘booking’, week 28 and during labour. Cohort B will follow 100 pregnant women who present with suspected sepsis in pregnancy or labour and will have at least two blood samples taken during their care pathway. Study blood samples will be collected during routine clinical blood sampling. Detailed medical history and physiological parameters at the time of blood sampling will be recorded, along with the results of routine biochemical tests, including C reactive protein, lactate and white blood cell count. In addition, study blood samples will be processed and analysed for transcriptomic, lipidomic and metabolomic analyses and both qualitative and functional immunophenotyping.Ethics and disseminationEthical approval has been obtained from the Wales Research Ethics Committee 2 (SPON1752-19, 30 October 2019).Trial registration numberNCT05023954.

Binding to Con A-Sepharose 4B of the low-affinity Fab fragment from sheep IgG1 anti-Dnp non-precipitating antibody was previously determined. This communication reports the results obtained when the concanavalin A interaction with Fd' fragments and L chains from non-precipitating and precipitating antibodies was examined. When Fd1 fragments and L chains from non-precipitating and precipitating antibodies were tested as inhibitors of the binding of 125I-labelled concanavalin A to guinea pig erythrocytes, inhibition of such binding was only achieved by Fd' fragments from non-precipitating antibodies. Forty eight per cent of this Fd' fragment was bound by Con A-Sepharose 4B. From these results and our previous studies we conclude that mannose and/or glucose residues must be present and exposed at the Fd' fragment from the low-affinity Fab arm of sheep IgG1 anti-Dnp non-precipitating antibody. Glycosylation differences may explain the difference in precipitation behaviour of the 2 types of antibody.