Microbiota of the first stool after birth

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Oulu University Hospital, lecture hall 12. Remote access: https://oulu.zoom.us/j/63230015162?pwd=VURvR1N4S09BekxkOVI5c0sxRVhJZz09

Topic of the dissertation

Microbiota of the first stool after birth

Doctoral candidate

Licentiate of Medicine Katja Kielenniva (o.s. Korpela)

Faculty and unit

University of Oulu Graduate School, Faculty of Medicine, PEDEGO Research Unit

Subject of study



Professor Pentti Huovinen, University of Turku


Professor Terhi Tapiainen, University of Oulu, Oulu University Hospital

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The role of the microbiota of the first stool after birth in later health

Meconium, a newborns’ first stool after birth, is the first easily available sample for gut microbiota studies. Recent studies have shown that first-pass meconium contains bacteria and that factors such as gestational age and delivery mode can impact meconium microbiota composition. The purpose of this thesis was to investigate what factors affect the bacterial composition of first-pass meconium and the impact of meconium microbiota on later health.

This was a prospective cohort study of 212 consecutive newborns. The first stool after birth was collected and analyzed using next-generation sequencing of the bacterial 16S rRNA gene. Fecal samples were also collected at one year of age. Clinical follow ups were conducted until the participants reached four years of age.

In total, 91% of the first-pass meconium samples contained bacterial DNA. The composition of first-pass meconium was distinct from that of the gut microbiota at one year of age. The biodiversity of the maternal living environment during pregnancy was associated with the bacterial composition of the first stool.

The bacterial composition of first-pass meconium was associated with the subsequent health of the infants. The infants with infantile colic had less lactobacilli in their meconium microbiota than those without colic. The children who were overweight at three years of age had less phylum Bacteroidetes and genus Bacteroides in their first-pass meconium than children with normal weight. The composition of intestinal microbiota at 1 year of age was not associated with the risk of being overweight in early childhood. The bacterial composition of meconium microbiota was not associated with subsequent atopic eczema or wheezing.

This thesis shows that earlier reported associations between intestinal microbiota, infantile colic, and overweight appear to be present immediately after birth. These findings emphasize the importance of pre- and perinatal factors on the early intestinal colonization and later health of children.
Last updated: 1.3.2023