Maternal circadian cortisol mediates the link between prenatal distress and breastfeeding.

Breastfeeding is associated with positive maternal and infant outcomes. It is recommended that women exclusively breastfeed for the first 6 months postpartum; however, these recommendations are not met in the majority of women. Psychological distress in pregnancy is associated with lower rates of breastfeeding initiation and duration in the postpartum period. The mechanisms linking maternal distress to breastfeeding are not understood. In this study we examined maternal circadian cortisol as a mechanism linking distress in pregnancy to breastfeeding. This study is a secondary data analysis of 197 pregnant women with singleton pregnancies who were part of a larger study of the effects of maternal mood on fetal and infant development. About 34% of women reported exclusively breastfeeding, 18% reported exclusively formula feeding, and 48% reported mixed feeding. Participants reported on perceived stress, perinatal anxiety and depression, and socioeconomic status during pregnancy. They provided salivary cortisol samples at three times a day for 3 days at 24, 30, and 36 weeks' gestation. Participants who reported lower socioeconomic status in pregnancy were less likely to breastfeed, and lower maternal cortisol awakening responses mediated this association. This area of research may identify foci in the prenatal period that could serve as targets for interventions to increase rates of breastfeeding. Lay summary Pregnant women who reported lower socioeconomic status in pregnancy were less likely to breastfeed. This association was mediated by lower cortisol awakening responses, but not evening cortisol levels, over pregnancy.