An observational study in Mastitis Postpartum, sponsored by University of Tromso. Recruiting at 2 sites in Norway. Open to female participants aged 18 Years to 50 Years. Per ClinicalTrials.gov, last updated 2026-03-12.
Sponsored by University of Tromso · Observational
The goal of this observational study is to gain more information about the aetiology and progression of mastitis and breast inflammation, in order to develop evidence-based clinical guidelines and treatment plans, especially concerning judicious use of antibiotics.
The main questions it aims to answer are:
Researchers will compare breastfeeding women with and without mastitis to see if the microbiological composition in milk and on the skin of the breast and breast nipple differs.
Mastitis (breast inflammation) is experienced by up to one-fifth of all breastfeeding mothers. Mastitis is a painful condition and a leading cause of early weaning, an undesired outcome with potentially negative implications for both mother and baby. Empirical evidence explaining the aetiology of mastitis is lacking; thus the definitions and treatment of mastitis is conflicting. The recent mechanobiological model proposes that the mechanical forces of lactation, especially at the onset of milk production, can cause damage to the mammary tissue, which induces an inflammatory response. Concurrently a growing amount of evidence shows that bacteria previously written off as contaminants have a role in mastitis which has been overlooked. The dynamics between the mechanobiological model and bacterial colonization have not yet been investigated. To fill this knowledge gap, researchers will conduct a longitudinal study collecting milk samples and questionnaires during the breastfeeding period with a particular emphasis on mastitis. Milk and skin swab samples will be used for culture dependent and culture independent assessment of the microbial composition in mastitis, and will be compared to the composition found in mothers without mastitis.
The main objective of this clinical study is to gather empirical data to provide an evidence-based update to the clinical guidelines for mastitis diagnosis and care. This will provide a foundation for improving the treatment and prevention of mastitis, with better outcomes for mothers and newborns.
31 studies on the registry are indexed under Mastitis; 7 are open to participants now.
This study's planned enrollment of 300 is above the median of 211 across 14 observational studies indexed under Mastitis.
Browse Mastitis studies →University of Tromso is the lead sponsor of 60 studies on the registry; 6 are open to participants now.
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Pregnant mothers aged > 18 years planning to give birth at University Hospital Noth Norway (UNN), with the intention to breastfeed and with an address in Tromsø municipality.
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Exclusion Criteria:
In this study breastfeeding mothers will be included. Samples will be collected from breast-feeding mothers experiencing mastitis Samples will be collected from breast-feeding mothers after the mastitis episode is resolved Breastfeeding mothers will be sampled at each mastitis episode, and with the final sample collected after a maximum of 12 months
Determination of the microbial composition in human milk from mothers without mastitis by MALDTI-TOF and Illumina sequencing
In order to investigate if there is a particular microbial composition of the human milk that leads to mastitis, the microbial composition in human milk from mothers without mastitis will be assessed. The investigators will collect milk samples from all enrolled mothers at day 6-7 after birth. Milk samples will be stored at -20 until further processing. Mothers who develop mastitis will be further sampled as described in outcome 2. Samples will be analyzed using culture dependent and culture independent methods. Following culturing of the milk samples, colonies will be analysed by Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) to identify bacterial species. DNA will be isolated from the same milk sample.16S rRNA amplicon sequencing of DNA from milk samples will be performed using the Illumina technology, in order to get an overview of the total bacterial composition.
Time frame: 18 months
Determination of the microbial composition in human milk from mothers at onset of mastitis by MALDTI-TOF and Illumina sequencing
The investigators will investigate if the microbial composition in human milk changes at onset of mastitis. By analysing possible changes in microbial composition the investigators will assess if the mastitis symptoms are caused by microorganisms, or if the symptoms of mastitis are inflammatory. Milk samples will be collected by the mother at onset of mastitis, 24 hours after onset of symptoms and after resolution of symptoms. If the mastitis episode is treated with antibiotics, a new sample will be taken 24 hours after cessation of antibiotic treatment. Milk samples will be stored at -20 until further processing. Samples will be analyzed using culture dependent, and culture independent methods. Following culturing of the samples, colonies will be analysed by MALDI-TOF to identify bacterial species. 16S rRNA amplicon sequencing of DNA from milk samples will be performed using the Illumina technology, in order to get an overview of the total bacterial composition.
Time frame: 18 months
Assessment of the microbial composition on nipples of mothers without mastitis
It is no agreement on if mastitis causing bacteria originate from the breast nipple, or if they are part of the milk microbiome. We will sample the breast nipples in order to investigate if microorganisms colonizing the breast skin enter the mammary glands, and potentially cause mastitis. A skin swab of the nipple (both breasts) will be taken at day 6-7 after birth. Following culturing of the swab, bacterial colonies will be analysed by MALDI-TOF to identify bacterial species. The skin swabs will be collected at the same timepoints as collection of milk samples.
Time frame: 18 months
Assessment of the microbial composition on nipples of mothers with mastitis
It is no agreement on if mastitis causing bacteria originate from breast nipple, or if they are part of the milk microbiome. We will sample the breast nipples in order to investigate if microorganisms colonizing the breast skin enter the mammary glands, and potentially cause mastitis. When the mother experiences symptoms of mastitis the mother will collect a skin swab sample. Following culturing of the swab, bacterial colonies will be analysed by MALDI-TOF to identify bacterial species. The skin swabs will be collected at the same timepoints as collection of milk samples.The microbial composition on nipples of mothers with mastitis will also be compared to the nipple microflora of mothers without mastitis in order to see if there is a correlation between particular skin colonizing bacteria that cause mastitis.
Time frame: 18 months
The concentration of immunological markers in milk from mothers without mastitis
A milk sample will be collected at day 6-7 after birth, and the concentration of immunological markers will be assessed in the milk of mothers without mastitis. The concentration (pg/ml) of 8 immune factors, including innate immune factors (IL6, IFNγ, TNFα), acquired immune factors (IL2, IL4, IL10), chemokines (IL8), and growth factor (GMCSF), will be determined by magnetic bead-based multi- plex immunoassays, using a Bioplex 200 instrument (Bio-Rad, Hercules, CA, USA).
Time frame: 18 months
The concentration of immunological markers in milk from mothers with mastitis
In order to determine if there is an increase in the immunological markers present in milk from mothers with mastitis, milk samples will be collected at onset of mastitis symptoms and 24 hours after cessation of symptoms. If the mother requires antibiotic treatment , samples will be collected at onset of treatment and 24 hours after cessation of antibiotic treatment. The concentration (pg/ml) of 8 immune factors, including innate immune factors (IL6, IFNγ, TNFα), acquired immune factors (IL2, IL4, IL10), chemokines (IL8), and growth factor (GMCSF), will be determined by magnetic bead-based multi- plex immunoassays, using a Bioplex 200 instrument (Bio-Rad, Hercules, CA, USA).The investigators will assess if the concentration of immunological markers differs in bacterial mastitis and inflammatory mastitis.
Time frame: 18 months
Mapping of mastitis symptoms by detailed Questionnaires
The mothers will be asked to fill in a detailed questionnaire regarding breastfeeding practice and symptoms of mastitis. The questionnaire will accompany the collection of milk samples as described in outcome 1and 2.
Time frame: 18 months
Plan to share: Yes — Researchers will share questionnaires, Informed consent forms and protocol, after data is published.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form
Time frame: Data will become available after publication
Access criteria: Access upon request
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University of Tromso