Identifying microbiome-based changes and biomarkers prior to disease development in mother and child, with a focus on gestational diabetes mellitus: protocol for the DANish Maternal and Offspring Microbiome (DANMOM) cohort study

Introduction The human gut microbiota is associated with gestational diabetes mellitus (GDM), which imposes a risk of developing long-term health problems for mother and child. Most studies on GDM and microbiota have been cross-sectional, which makes it difficult to make any conclusions on causality. Furthermore, it is important to assess if a dysbiotic microbiota is passed from the mother to the child, and then being at risk of developing metabolic health problems later in life. The DANish Maternal and Offspring Microbiome study aims to identify gut microbiota-related factors involved in metabolic dysfunction in women with GDM and their offspring. Importantly, the study design allows for early detection of biological changes associated with later development of metabolic disease. This could provide us with unique tools to support early diagnosis or implement preventative measures.Methods and analysis Pregnant women are included in the study after the 11–14 weeks’ prenatal ultrasound scan and followed throughout pregnancy with enrolment of the offspring at birth. 202 women and 112 children have been included from North Denmark Regional Hospital and Aalborg University Hospital in Denmark. Mother and child are followed until the children reach the age of 5 years. From the mother, we collect faeces, urine, blood, saliva, vaginal fluid and breast milk samples, in addition to faeces and a blood sample from the child. Microbiota composition in biological samples will be analysed using 16S rRNA gene sequencing and compared with demographic and clinical data from medical charts, registers and questionnaires. Sample and data collection will continue until July 2028.Ethics and dissemination The study protocol has been approved by the North Denmark Region Committee on Health Research Ethics (N20190007). Written informed consent is obtained from all participants prior to study participation. Study results will be published in international peer-reviewed journals and presented at international conferences. The results will also be presented to the funders of the study and study participants.