Influence of intra- and extrauterine factors on infant sleep in the first 6 months of life()

OBJECTIVE: Infant sleep problems can affect the child's health. Maternal characteristics have been associated with the quality of infant sleep, but few studies have investigated the impact of intrauterine conditions. The aim of the study was to evaluate the association between adverse intrauterine environments (maternal smoking, hypertension, diabetes, and intrauterine growth restriction) and extrauterine factors on infant sleep in the first 6 months of life. METHODS: Prospective cohort study, including singleton and at-term infants. Mothers were interviewed after delivery and at 30 days, 3 months, and 6 months of life. Socioeconomic, breastfeeding, and sleep data were self-reported by mothers using semi-structured interviews. Maternal stress (Perceived Stress Scale) and postpartum depression symptoms (Edinburgh Postpartum Depression Scale) were assessed. RESULTS: There was no statistically significant association between intrauterine environments and the sleep of infants of the 359 mother–child dyads investigated. Total infant sleep time decreased from approximately 13–11 h from 30 days to 6 months of age (p < 0.001) and the longest period of uninterrupted sleep increased from approximately 4–6 h during the same period (p < 0.001). Breastfed infants slept longer in 24-h periods in the first month, but they woke up more often throughout the night when compared to infants receiving formula. Mothers with depressive symptoms reported increased sleep latency time. CONCLUSIONS: Adverse intrauterine environments did not significantly affect sleep measures in the first 6 months of life. Maternal characteristics and practices, however, were associated with infant sleep, suggesting that environmental factors significantly contribute to sleep quality early in life.