Infant Sleep Behaviour and Gut Microbacteria

Inclusion Criteria: * Good general health status * exclusively breastfed (at baseline) * vaginal birth delivery mode Exclusion Criteria: * C-section delivery mode * Formula fed (at baseline) * Diseases or lesions of the central nervous system, acute pediatric disease, developmental/neurologic/metabolic disorders, chronic medical conditions, or head injury * Family history of narcolepsy/psychosis/bipolar disorder * Conceptual age of \< 37 or \> 42 weeks * Low birth weight (\< 2500g) * Co-sleeping during \> 50% of the time in the same bed * Medication use affecting sleep/alertness * Vaccination (2 weeks prior to study) * Antibiotics (3 months prior to study) * Travelling across a time zone (within 1 month prior to study) * intrauterine drug exposure, intrauterine infection, known or suspected drug or alcohol abuse * Insufficient knowledge of German (parents)