The LITTLE OWLS Study (in German: "Kleine Eulen OWL"): Exploring the Early-life Microbiome Development and Physical and Mental Health Outcomes During Childhood. (LITTLE OWLS)

Analysis of microbiota composition, diversity, (function) using next-generation sequencing (primarily: 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Fecal metabolome analysis using targeted/ untargeted mass-spectrometry methods.

Analysis of microbiota composition, diversity, (function) using next-generation sequencing (primarily 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Analysis of microbiota composition and diversity using next-generation sequencing (primarily 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Analysis of microbiota composition and diversity using next-generation sequencing (primarily 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Analysis of microbiota composition and diversity using next-generation sequencing (primarily 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Changes in gut microbiome composition, diversity, (function) following perturbations by antibiotic use analyzed by next-generation sequencing (primarily 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Changes in gut microbiome composition, diversity, (function) following perturbations by gastrointestinal infections analyzed by next-generation sequencing (primarily 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Physician-diagnosed allergy (wheeze, allergic rhinitis, food allergy). From 2-years of age allergic symptoms are further recorded during the annual study examinations using the ISAAC questionnaire.

Physician-diagnosed atopic dermatitis/ eczema. From 1-year of age the skin status of each study child is further screened based on SCORAD (SCORing Atopic Dermatitis). The score evaluates three distinct areas: extend, intensity, subjective symptoms. The overall score ranges from 0 to 103: < 25: Mild Atopic Dermatitis, 25 - 50: Moderate Atopic Dermatitis, > 50: Severe Atopic Dermatitis.

Physician-diagnosed asthma. From 2-years of age, asthmatic symptoms are further recorded during the annual study examinations using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire (calculating the percentage frequencies of wheezing, eczema, and rhinitis symptoms over the last 12 month).

Physician-diagnosed overweight or obesity. Further the Body Mass Index (kg/m²) is calculated for each study child (annually) as weight (kg) divided by the square of length or height (in meters).

Physician-diagnosed functional gastrointestinal disorders (like chronic constipation, diarrhea or irritable bowel syndrome (IBS). From 1-year of age, functional gastrointestinal symptoms are further recorded during the annual study examinations using the R4PDQ questionnaires (Rome foundation) according to the Rome IV criteria (1-3 years; 4 years +). The R4DQ uses a mix of Likert-type scales, yes/no, and multiple-choice questions to assess symptom severity and frequency. Scoring varies by module, with no universal cut-off scores.

Number of respiratory, gastrointestinal, ear/ eye or urinary tract infections per year

Bowel habits measured by stool frequency, stool consistency and stool colour. Bowel habit information and Bristol Stool Scale scores are documented with each fecal sample collection (Type 1-7, hard-watery).

Number of health care visits, hospitalizations, or disease diagnoses per year.

Weight in kg.

Height in cm

Head circumference in cm

Child developmental milestones are examined during the annual study visits using pediatric questionnaires (German: "Grenzsteine der kindlichen Entwicklung") for cognitive, motor, socio-emotional and verbal development.

Mother-infant bonding is assessed at 4 weeks after birth using the Postpartum Bonding Questionnaire (PBQ). The PBQ uses a 6-point Likert scale (0 = Always to 5 = Never), yielding a maximum total score of 125. High scores indicate greater bonding difficulties, while low scores indicate a healthy mother-infant relationship.

The infant temperament development of the child is examined using the Infant Behavior Questionnaire (IBQ) at 6 month of age. Parents rate behaviors observed over the past week or two on a 7-point Likert scale (from 1 = never to 7 = always, plus a "does not apply" option). Scale scores are calculated as the mean score of all applicable items answered (excluding "does not apply" choices). Scores are independently rated for each of the 6 Core Temperament Dimensions: Activity Level, Soothability, Fear, Distress to Limitations, Smiling and Laughter, Duration of Orienting. Higher mean scores indicate a greater frequency of that specific behavioral temperament trait.

The infant crying behaviour is examined using the Infant Behavior Questionnaire (IBQ) at 6 month of age. Parents rate behaviors observed over the past week or two on a 7-point Likert scale (from 1 = never to 7 = always, plus a "does not apply" option). Scale scores are calculated as the mean score of all applicable items answered (excluding "does not apply" choices). Scores are independently rated for each of the 6 Core Temperament Dimensions: Activity Level, Soothability, Fear, Distress to Limitations, Smiling and Laughter, Duration of Orienting. Higher mean scores indicate a greater frequency of that specific behavioral temperament trait.

Coping behaviour of children is assessed annually using the Emotional regulation/ impulse management questionnaire (IMMA-6 short version) starting from 1 year of age. The calculation of results follows standard psychometric scoring rules for 6-point Likert-scale questionnaires. The three main scales (core dimensions) are evaluated: 1) Child's Self-Regulation (C-Scale), 2) Parental Co-Regulation (P-Scale), 3) Parental Expectations/Goals (E-Scale)

Emotional regulation of children is assessed annually using the Pediatric Symptom Checklist (IMMA) starting from 1 year of age. The calculation of results follows standard psychometric scoring rules for 6-point Likert-scale questionnaires. The three main scales (core dimensions) are evaluated: 1) Child's Self-Regulation (C-Scale), 2) Parental Co-Regulation (P-Scale), 3) Parental Expectations/Goals (E-Scale)

General psychosocial functioning in children (and potential emotional and behavioral difficulties) is examined using the Pediatric Symptom Checklist (PSC-35). The Pediatric Symptom Checklist (PSC) is scored by assigning points to each response (0 for "never", 1 for "sometimes", and 2 for "often") calculating a total score. A total score of 24 or higher (from 3-6 years) indicates a positive screening result for psychosocial impairment. If four or more items are left blank, the questionnaire is considered invalid and cannot be scored.

Analysis of microbiota composition, diversity, (function) using next-generation sequencing (primarily: 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing). The mothers' stool samples will continue to be collected annually after the first year of life until the end of the breastfeeding period (on an individual basis for each mother). In addition, a stool sample will be collected and analyzed 1-3 days after the last breastfeeding session and 4 weeks thereafter.

Fecal metabolome analysis using targeted/ untargeted mass-spectrometry methods.

Analysis of microbiota composition, diversity, (function) using next-generation sequencing (primarily: 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing). The mothers' milk samples will continue to be collected annually after the first year of life until the end of the breastfeeding period (on an individual basis for each mother).

Human milk metabolome analysis using targeted/ untargeted mass-spectrometry methods.

Analysis of microbiota composition, diversity, (function) using next-generation sequencing (primarily: 16S rRNA- amplicon sequencing; partially: ITS-amplicon sequencing, whole metagenome shotgun sequencing).

Parental mental health is analysed for perceived stress using the Perceived Stress Scale Questionnaire (PSS-10). The PSS-10 evaluates how unpredictable, uncontrollable, and overloaded a person has found their life over the past month. The final total score will range from 0 to 40. Higher point values represent a higher level of perceived stress.

Parental mental health is analysed for depression using the Patient Health Questionnaire (PHQ-9). The PHQ-9 scores depressive symptom severity over the past two weeks using a 0 to 27 point scale. A score of 10 or higher is generally considered the threshold for a positive screening, warranting further clinical evaluation.

Parental mental health is analysed for anxiety using the Generalized Anxiety Disorder scale (GAD-7). The GAD-7 scoring and analysis scheme calculates a single cumulative severity score ranging from 0 to 21 by summing the ratings of seven individual items. The Cut-Off of ≥ 10 serves as the standard threshold for identifying probable cases of Generalized Anxiety Disorder.