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This study investigates whether the timing of feeding expressed breast milk influences infant sleep and circadian (day-night) development in preterm infants.
In early life, infants produce very little of the hormone melatonin, which plays a key role in regulating sleep and circadian rhythms. Breast milk naturally contains melatonin, and its levels vary across the day, with higher concentrations at night. This variation may provide important biological signals that help infants develop healthy sleep-wake patterns.
However, expressed breast milk is often fed without considering the time it was expressed. This may disrupt the transfer of circadian signals from mother to infant.
The aim of this randomised controlled trial is to determine whether feeding expressed breast milk according to the time of expression (e.g. giving night-time milk at night) improves sleep consolidation and circadian development compared with usual feeding practices.
A total of 200 preterm infants born between 32+0 and 36+6 weeks' gestation who are receiving expressed breast milk will be enrolled and randomly assigned to one of two groups:
Intervention group: preterm infants receive expressed breast milk matched to the time of day it was expressed (day, evening or night)
Control group: preterm infants receive expressed breast milk without regard to timing (usual practice)
The main outcome is sleep consolidation at 6 months of age, measured objectively using actigraphy (a small wearable device that records sleep and activity). Additional outcomes include sleep patterns over time, circadian development, melatonin exposure, gut microbiota composition, and clinical outcomes such as infections and neurodevelopment.
The intervention does not involve any medication and uses the infant's usual nutrition. Risks are minimal and mainly relate to the additional effort required for milk labelling and timing.
This study will provide evidence on whether a simple, low-risk change in feeding practice can support infant sleep and early-life circadian development, with potential benefits for child health and family well-being.
This study investigates whether the timing of feeding expressed breast milk influences infant sleep and circadian (day-night) development in preterm infants.
In early life, infants produce very little of the hormone melatonin, which plays a key role in regulating sleep and circadian rhythms. Breast milk naturally contains melatonin, and its levels vary across the day, with higher concentrations at night. This variation may provide important biological signals that help infants develop healthy sleep-wake patterns.
However, expressed breast milk is often fed without considering the time it was expressed. This may disrupt the transfer of circadian signals from mother to infant.
The aim of this randomised controlled trial is to determine whether feeding expressed breast milk according to the time of expression (e.g. giving night-time milk at night) improves sleep consolidation and circadian development compared with usual feeding practices.
A total of 200 preterm infants born between 32+0 and 36+6 weeks' gestation who are receiving expressed breast milk will be enrolled and randomly assigned to one of two groups:
Intervention group: preterm infants receive expressed breast milk matched to the time of day it was expressed (day, evening or night) Control group: preterm infants receive expressed breast milk without regard to timing (usual practice)
The main outcome is sleep consolidation at 6 months of age, measured objectively using actigraphy (a small wearable device that records sleep and activity). Additional outcomes include sleep patterns over time, circadian development, melatonin exposure, gut microbiota composition, and clinical outcomes such as infections and neurodevelopment.
The intervention does not involve any medication and uses the infant's usual nutrition. Risks are minimal and mainly relate to the additional effort required for milk labelling and timing.
This study will provide evidence on whether a simple, low-risk change in feeding practice can support infant sleep and early-life circadian development, with potential benefits for child health and family well-being.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Chronobiologically Timed Feeding of Expressed Breast Milk | Experimental | Infants receive expressed breast milk that is administered according to the time of expression (day, evening, or night), aligning feeding with circadian timing. |
|
| Usual Feeding Practice (Untimed Expressed Breast Milk) | Active Comparator | Infants receive expressed breast milk without regard to the time of expression (standard care). |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Chronobiologically Timed Feeding of Expressed Breast Milk | Other | Expressed breast milk is labelled at the time of expression and categorised into predefined time windows: Day milk: 06:00-17:59 Evening milk: 18:00-21:59 Night milk: 22:00-05:59 Infants are fed milk corresponding to the appropriate time-of-day window to align feeding with circadian rhythms. Caregivers receive standardised training, and adherence is monitored using feeding logs. |
| Measure | Description | Time Frame |
|---|---|---|
| Sleep consolidation (longest nocturnal sleep bout) | Measured by actigraphy | At 6 months of age |
| Measure | Description | Time Frame |
|---|---|---|
| Sleep fragmentation | Assessed by actigraphy and sleep-wake diaries | At 2, 4, 6, 12, and 24 months |
| Circadian rhythm development (day-night activity ratios and circadian function index) | Assessed by actigraphy |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Petra Zimmermann, MD, PhD | Contact | +4141 205 82 69 | petra.zimmermann@luks.ch |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Kantonsspital Luzern, Universität Luzern | Lucerne | Switzerland |
Anonymised microbiome data will be made openly available in a recognised public repository (e.g. European Nucleotide Archive (ENA)).
Clinically diagnosed infections (including otitis media and lower respiratory tract infections), assessed via medical records and parental report.
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|
| Usual Feeding Practice (Untimed Expressed Breast Milk) | Other | Expressed breast milk is fed without consideration of the time of expression. Milk handling, storage, and preparation follow standard procedures. No modification of milk composition or additional substances are introduced. |
|
| At 2, 4, 6, 12, and 24 months |
| Parent-reported sleep outcomes | Assessed using the Brief Infant Sleep Questionnaire (BISQ) | At 2, 4, 6, 12, and 24 months |
| Melatonin circadian profiles | In breast milk and infant stool | At 2, 4, 6, 12, and 24 months |
| Intestinal microbiota composition | Assessed by shotgun metagenomic sequencing | At 2, 4, 6, 12, and 24 months |
| Infection rates | Clinically diagnosed infections (including otitis media and lower respiratory tract infections), assessed via medical records and parental report | At 2, 4, 6, 12, and 24 months |
| Neurodevelopmental outcomes | Bayley Scales of Infant and Toddler Development (Bayley-III) | 24 months |