Maternal Circadian Rhythm and Its Association With Meal Timing and Density: A Prospective Cohort Study

OBJECTIVES: The aim of this study was to determine the change of melatonin rhythm in pregnant women across gestation and its association with chrononutrition characteristics. METHODS: This was a prospective cohort including 70 healthy primigravidas. During the second and third trimesters, pregnant women provided salivary samples collected at 9:00, 15:00, 21:00, and 3:00 h over a 24 h day for melatonin assay. Data on chrononutrition characteristics were collected using 3-day food record. A rhythmic melatonin secretion over the day that remained stable across trimesters was observed among the pregnant women. RESULTS: In the second trimester, higher energy intake during 12:00–15:59 h and 19:00–06:59 h predicted a steeper melatonin AUCI (β = −0.32, p = 0.034) and higher AUCG (β = 0.26, p = 0.042), respectively. Macronutrient intake within 12:00–15:59 h was negatively associated with mean melatonin (Fat: β = −0.28, p = 0.041) and AUCG (Carbohydrate: β = −0.37, p = 0.003; Protein: β = −0.27, p = 0.036; Fat: β = −0.32, p = 0.014). During the third trimester, a shorter eating window predicted higher melatonin mean (β = −0.40, p = 0.007), peak (β = −0.41, p = 0.007), and AUCG (β = −0.43, p = 0.003). A flatter AUCI across trimesters was associated with reduced carbohydrate intake during 12:00–15:59 h (β = −0.40, p = 0.026). CONCLUSIONS: Our findings suggest that energy and macronutrient intakes particularly during 12:00–15:59h and 19:00–06:59h and the length of feeding period during gestation can influence maternal melatonin rhythm and output. This indicates the potential of time-based dietary approach to alter circadian rhythm in pregnant women.