Gestational age at birth is one of the major indicators used to assess newborn mortality and morbidity, and the World Health Organization classifies the maturity of newborns at birth into premature, full-term, and postmature[1]. Among the premature, late preterm birth is defined as birth at the gestational ages between 34 weeks and 36 weeks[2].

Statistics Korea classifies late preterm births in Korea as infants at the gestational ages between 32 and 35 weeks, or at 36 weeks, which makes it difficult to identify the exact number of newborns at the gestataional ages between 34 and 36 weeks. Premature births in Korea were estimated at 30,376 and among those premature newborns, the births at the gestational ages between 32 and 36 weeks were estimated at 26,721, which is 88% of all the delivered premature babies in 2012[3]. The lack of concern and attention of health care providers may be due to the physical maturity and health condition of the late preterm infants being so similar to those of full-term infants, whereby the majority of late preterm infants (LPIs) are discharged from hospitals after receiving general medical and nursing care management tailored for full-term infants. However, the onset of breastfeeding for LPIs is delayed longer than that for full-term infants[4], and the rates of breastfeeding at home at the 4th week after discharge appeared to be lower[5]. In addition, LPIs are more likely to be re-hospitalized due to health problems such as jaundice or other infectious diseases caused by mothers’ inexperience or a lack of feeding techniques[6-9], all of which require health care providers to furnish the LPIs with more effective intervention for breastfeeding. Despite the fact that LPIs are the majority of premature newborns, there has been little research by healthcare providers in Korea[6,7,10,11] addressing breastfeeing for LPIs.

There are several reasons why health care providers should focus on the promotion of breastfeeding for late preterm infants. First, the birth rate in Korea has steadily decreased over the past three or four decades, while the proportion of premature and late preterm newborns has consistently increased. This requires health care providers to have more concern for premature newborns. Second, the World Health Organization recommends that infants should be exclusively breastfed for the first six months[12], especially LPIs who did not receive immunological substances from the mother during the late phase of pregnancy due to premature labor. Breastmilk plays an essential role in preventing the late preterms which from getting infectious diseases[13]. Third, breastfeeding for LPIs depends on the infant’s health condition, especially respiratory problems which induce a delay in breasfeeding[14]. However, almost no hospitals in Korea have such guidelines tailored for the specific conditions of LPIs. Fourth, because the hospital stay of LPIs is shorter than that of premature infants under the gestational age of 34 weeks, the opportunity to provide breastfeeding education by health care providers is often inadequate[5]. Consequently, the prevalence of breastfeeding for LPIs was lower than that of prematures born at less than 34 weeks of gestational age[5,11] and the 36 week LPIs who had the shortest stay in hospital had the lowest breastfeeding rate[10].

In light of addressing such issues, this study was conducted to identify breastfeeding practice of LPIs until 12 weeks after discharge, and predictors influencing breastfeeding at the 12th week after hospitalization. The rationale for establishing the 12th week after discharge as the time point of identifying the predictors for breastfeeding is based on a study done by Jang et al.[11]. Jang et al.[11] conducted a cross-sectional study to identify the predictors of breastfeeding practice in mothers from 1 to 6 months after discharge, reporting that the mothers’ breastfeeding significantly decreased from three months after discharge, which suggested that better-organized longitudinal studies should be conducted to encompass a period from discharge to three months thereafter, in order to identify any changes in breastfeeding and to predict factors contributing to the exclusive breastfeeding.

Breastfeeding newborns until the age of two years plays an important role in providing nutritional requirements necessary for the proper growth and development of infants[12]. Breast milk has been scientifically proved to contain immunological and anti-infective factors that prevent intestinal diseases[18]. However, neither the exact number of breastfeeding of late preterms, nor standardized guidelines for age-appropriate breastfeeding have been established yet at the governmental level in Korea. Therefore, to provide baseline information to develop breastfeeding education tailored for the particular needs of LPIs, this study was done to identify breastfeeding practice with LPIs for 12 weeks after discharge, as well as predictors influencing exclusive breastfeeding practice at the 12th week after discharge.

One of the most important results of this study showed that 77.4% of LPIs were fed with the mixed feeding method during hospitalization. This was consistent with other studies conducted with full-term infants[19]. Jang and Kim[19] reported that nearly 20% of full-term newborns were fed exclusively with breast milk, while 80% were fed with the mixed feeding method. The general guidelines of educational programs for breastfeeding provided by the institutions are that nurses recommend supplementing breastfeeding with formula both for full-term and LPIs when mothers cannot fully feed colostrum to newborns due to the amount of colostrum not being sufficient. This led the majority of infants to be discharged with an experience of mixed feeding. In addition, because of LPIs’ lack of sucking and swallowing power, it is not only difficult to start breastfeeding within one hour after birth, but also to maintain exclusive breastfeeding until the time of discharge. This results in LPIs being discharged with mixed feeding, rather than exclusive breastfeeding, much more frequently than full-term infants[20,21].

Exclusive breastfeeding and formula feeding steadily increased, and mixed feeding decreased after discharge. This result is derived from the fact that the mothers who continued mixed feeding, changed to exclusive breastfeeding or formula feeding, moreover the change rate of mixed feeding to formula was higher than that to exclusive breastfeeding from mixed feeding. About 10.4% of mothers who breastfed their LPIs at the 4th week after discharge was far lower than what is recommended by World Health Organization[12]. This lower rate of breastfeeding practice for LPIs compared to full-term infants can be explained by the physiological effects of late preterm birth itself, which is considered the most important contributing factor for the failure of breastfeeding[22]. A multicenter study done by Medoff-Cooper et al.[23] with 802 LPIs at 14 hospitals in the United States and Canada, reported that although LPIs whose gestational age was close to full-term, they still had problems with feeding intolerance due to physiological immaturity, causing impairment of masseteric and sucking functions. A second reason for the lower rate of breastfeeding in this study can be explained by showing that mothers who gave birth to LPIs usually had premature labor due to health conditions caused by pregnancy induced hypertension, diabetes mellitus, or obesity. These health conditions inhibit secretion of prolactin in mothers, delaying breastfeeding compared to mothers who deliver full-term newborns[13,16]. The third reason is that most guidelines for breastfeeding used in clinical settings in Korea have been developed, focusing on mothers with full-term newborns, leaving mothers with LPIs with inadequate instruction. Furthermore, the extent to which educational programs for breastfeeding are given to mothers with LPIs often differ from unit to unit within individual hospitals. The final reason is that as the American Academy of Pediatrics[23] have reported that LPIs over the gestational age of 35 weeks were 2.2 times more likely to show jaundice when they were breastfed than full-term infants, resulting in rehospitalization due to jaundice or other infectious disease[9]. Consequently, some health care providers may be hesitant to recommend breastfeeding for LPIs as the best method. In light these issues, nurses should carefully assess LPIs’ clinical conditions, such as hypoglycemia, hypothermia, respiratory difficulty, or feeding intolerance, all of which may affect the desirability of breast feeding.

Finally, the factors that predict exclusive breastfeeding practice at the 12th weeks after discharge showed that mothers who had a vaginal delivery changed from formula feeding to mixed feeding or mixed feeding to exclusive breastfeeding 2.96 times more often than mothers who had Cesarean-section. Plus, late preterms who did not have any feeding intolerance were breastfed 3.03 times more than infants who had feeding intolerance, and LPIs who were fed mixed feeding during hospitalization had 7.84 times more exclusive breastfeeding than those who were fed formula. This result was consistent with another study[11]. Jang et al.[11] reported factors influencing breastfeeding for LPIs were the type of delivery and feeding method during hospitalization. Special consideration should be given to the effectiveness of breastfeeding during hospitalization, which can affect the continuation of breastfeeding after hospitalization up until the 12th week. Along with the provision of proper nursing care for health problems for both mothers and infants, education is one of the most important tools that nurses can use to promote breastfeeding LPIs during and after hospitalization. Unlike guidelines for full-term newborns who can be fed right after birth, the guidelines for LPIs who have to be hospitalized for a certain period of time should include special measures for stimulating the lactation process and the production of breast milk.

Breastfeeding LPIs in this study increased continuously from the 1st to the 12th week after discharge, but many mothers changed from mixed breastfeeding to formula feeding rather than breastfeeding exclusively. In addition, breastfeeding at the time of the 12th week after discharge was a major predictor indicating mothers who had breastfed their infants during hospitalization would be more likely to continue after hospitalization than their counterparts. These findings suggest that further research is needed to address the issues of developing more effective educational guidelines for breastfeeding, tailored to the specific needs of LPIs, with a particular focus on how to convert mothers who feed their infants with mixed feeding after hospitalization, to change to exclusive breastfeeding.

Several limitations of this study may be worthy of discussion. First, this study included only two hospitals in Korea and the results cannot be considered definitive. However, considering the importance of breastfeeding for the LPIs, these hospitals were carefully selected to represent strong support for promoting breastfeeding in Korea. To compare the variations of educational guidelines for breastfeeding, further study is needed to include general practices of breastfeeding at all Korean hospitals, not just at the hospitals in this study. Another limitation of this study is that it did not include underlying psychological factors that could play a key role in predicting successful practice of breastfeeding in mothers with LPIs, such as self-efficacy or empowerment. Finally, this study contained a relatively small sample size of LPIs and their mothers. In order to confirm of the findings in this work, more replicated studies are needed to include different mother-infant dyads at different clinical settings, as well as studies to collect data on breastfeeding appropriate for government use.

Breast milk contains nutritional substances essential for LPIs. For this reason, breastfeeding is recommended as the healthiest source of nutrition for LPIs. Consequently, our study was conducted to identify breastfeeding LPIs during the 1st to the 12th week after discharge, as well as factors influencing exclusive breastfeeding practice at the 12th week after discharge. Exclusive breastfeeding in LPIs had continuously increased for the period of 12 weeks after they were discharged from the hospital, and the mixed feeding method at the time of discharge changed to formula feeding exclusively over time, which indicated that educational programs to promote breastfeeding should be focused on how to continue exclusive breastfeeding for at least 12 weeks after discharge. Furthermore, mothers’ breastfeeding during hospitalization affected the practice of breastfeeding at 12th week after discharge. Therefore, special consideration in education should be given to mothers with LPIs in addition to more effective methods of breastfeeding at the hospital and at home. The significance of this study includes an attempt to provide practical information on appropriate times and directions for breastfeeding interventions targeted for mothers who have not been instructed properly, due to a lack of established guidelines in Korea.