In plain words
Melatonin is a hormone the brain makes in response to darkness. It helps set the body's sleep and wake clock. A baby's own melatonin rhythm develops over the first few months, which is one reason days and nights can feel mixed up. Melatonin also passes into breast milk, and levels there tend to be higher at night. Researchers study it as one of several sleep-related compounds in milk. Melatonin is also sold as a supplement for adults. Whether it has any role for babies or in pregnancy is a question for your provider. Its role in milk is still being studied.
The deeper version
Melatonin is synthesized from serotonin in the pineal gland, with secretion driven by the suprachiasmatic nucleus and suppressed by light. Infant secretion becomes entrained to a pattern over the first months of life. Human milk contains melatonin with a nocturnal peak. Italianer and colleagues (Nutrients, 2020) reviewed circadian variation in milk composition, including melatonin, tryptophan, and cortisol, which is highest in morning milk. The clinical relevance of milk melatonin to infant sleep is not established. Melatonin is used in some pediatric and neurodevelopmental settings, and its use in pregnancy and infancy outside those settings is not established. The controversy is whether milk melatonin has a meaningful physiological effect on the infant.
Where it comes up
- Breastfeeding and sleep: feeding to sleep, night feeds, and sharing the loadFeeding Your Baby
- Days and nights mixed upBaby Basics
- Fussy weeks and developmental changesBaby Basics
- Sleep deprivation: what it does and how to survive itPostpartum: Your Body
What mothers here say about melatonin
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Sources
- Italianer MF and colleagues — Circadian variation in human milk composition, a systematic review, Nutrients (2020)