Breastfeeding of preterm infants. Associated factors in infants, mothers, and clinical practice.

Abstract: Breastfeeding has even more pronounced health benefits for preterm infants than for full-term infants, but preterm infants are less breastfed. There is no consensus in Danish neonatal intensive care units (NICUs) about which clinical methods facilitate breastfeeding. Skin-to-skin contact between infant and parent is the first step in the breastfeeding process for preterm infants, but studies of toleration of skin-to-skin contact in extremely preterm infants – less than 28 gestational weeks – are sparse. The overall aim of this thesis was to study and identify factors associated with breastfeeding of preterm infants, in infants, mothers and clinical practice in order to gain more knowledge of how to guide mothers of preterm infants in breastfeeding. This thesis is based on three studies: Study A, a clinical intervention study with 22 clinically stable extremely preterm infants that investigated infants’ tolerance of skin-to-skin contact with their parents; Study B, a national survey of breastfeeding support at all Danish NICUs; and Study C, a national prospective cohort study of breastfeeding preterm infants with the participation of 1,221 mothers and their 1,488 preterm infants at a gestational age of 24-36 weeks. Regression analyses were used to investigate factors associated with early establishment of exclusive breastfeeding, exclusive breastfeeding at discharge and adequate duration in accordance with the Danish Health and Medicines Authority’s recommendations. The results showed that the extremely preterm infants in Study A, with mean weight 702 grams, tolerated skin-to-skin contact with their parents with no significant differences in mean skin temperature, heart rate, respiration rate, or oxygen saturation before, during, and after skin-to-skin contact. In Study B, the NICUs reported that they aimed for early skin-to-skin contact, and in 81% of the infants, skin-to-skin contact was initiated within the first 24 hours of life, but significantly fewer of the extremely preterm infants did so. In Study B, the NICUs described support of breastfeeding as being highly prioritised, reflected in skin-to-skin contact and parents’ presence at the NICU, recommendations of breast milk expression, supplementation feedings via feeding tubes, and avoidance of the use of infant feeding bottles as a common practice. Of the 1,488 preterm infants in Study C, 99% initiated breastfeeding, at discharge, 68% were exclusively breastfed, 17% were partially breastfed, and 31% were exclusively breastfed for an adequate duration following discharge. Factors in infants, mothers and clinical practice were associated with exclusive breastfeeding. Extremely preterm infants and multiples established exclusive breastfeeding at a higher postmenstrual age (PMA) and had twice the odds of not being exclusively breastfed at discharge. Mothers with low and intermediate education, with less breastfeeding experience, or who smoked had higher odds of inadequate duration of exclusive breastfeeding. Admitting mothers to the NICU together with the infant immediately after delivery was associated with 1.5 (95% CI 0.3-2.6) days earlier establishment of exclusive breastfeeding. Initiation of breast milk expression showed a dose-response effect: the later the initiation, the higher the odds ratio (OR) for failure of exclusive breastfeeding at discharge and inadequate duration of exclusive breastfeeding. Nipple shield use was associated with failure of exclusive breastfeeding at discharge (OR 2.3 (95% CI 1.6-3.2)) and inadequate duration of exclusive breastfeeding (OR 1.4 (95% CI 1.1-1.9)). Minimising the use of a pacifier during breastfeeding establishment was associated with 1.2 (95% CI 0.1-2.3) days earlier establishment of exclusive breastfeeding and showed a protective effect for exclusive breastfeeding at discharge (OR 0.4 (95% CI 0.3-0.6)). Test weighing the infant also showed a protective effect for exclusive breastfeeding at discharge (OR 0.6 (95% CI 0.4-0.8)). Breastfeeding milestones were generally reached at different PMAs for various GA groups, but preterm infants were able to initiate breastfeeding early, with some delay in infants less than GA 32 weeks. The results indicate that it is possible to establish early skin-to-skin contact with clinically stable extremely preterm infants. Danish preterm infants initiate breastfeeding to the same extent as full-term infants. Breastfeeding competence is not developed at a fixed postmenstrual age, but is influenced by multiple factors in infants, mothers and clinical practice. Admitting mothers to the NICU immediately after delivery seems to contribute to earlier establishment of exclusive breastfeeding. Minimising the use of pacifiers during breastfeeding establishment, restricting the use of nipple shields, encouraging early initiation of breast milk expression, and test weighing of infants may facilitate exclusive breastfeeding in preterm infants. More support and attention should be given to groups with a higher risk for failure of exclusive breastfeeding: preterm infants with a gestational age of less than 32 weeks, multiples, mothers who smoke, have lower education or less breastfeeding experience.