LAUSR

Breast milk cortisol concentration varies among and within lactating women, but the causes and consequences of variation are not yet fully understood. This study investigated whether maternal fasting from food and water for over 16 h per day during the third trimester of pregnancy was associated with increased concentrations of cortisol in colostrum during the month of Ramadan in a Moroccan sample. Participants were women who gave birth at the public maternity hospital in Rabat, Morocco throughout the month of and month following Ramadan. Participants completed interviews (N = 92), underwent anthropometric assessment (N = 73), and colostrum samples (N = 63) were collected approximately 48–72 h postpartum. Cortisol analysis was completed on a subset of colostrum samples (N = 43). Women were categorized as fasting every day of Ramadan before giving birth (N = 52/92, 57%), fasting some days (N = 29/92, 32%), and not fasting (N = 11/92, 11%). For women who fasted, average fasting duration was 19.5 days (range: 1–29 days), and average time between the last day of fasting and birth was 8.8 days (range: 0–43 days). The number of days of fasting was positively associated with cortisol concentrations in colostrum (p < .009) in a multivariate analysis controlling for maternal anthropometry, hypertension and/or diabetes, and reasons for opting out of fasting. Each day of fasting was associated with a 4.05% increase in colostrum cortisol. Results are consistent with the hypothesis that maternal fasting during the third trimester of pregnancy increases breast milk cortisol and thus alters the hormonal milieu to which the infant is exposed.