Composition and fortification of human milk influence gastroesophageal reflux in preterm infants.

Aims. Human milk (HM) is considered a better choice than formula also for preterm infants’ nutrition, because it provides unique nutritional components, contributes to host defences, exerts trophic effects on gastrointestinal tract and promotes maternal-infant bonding; furthermore, feeding human milk to preterm infants may lead to short and long term beneficial effects. However, both preterm milk and banked term human milk provide insufficient amount of energy and essential nutrients needed for rapid growth and normal development as if infant had remained in uterus. For this reason, preterm HM is usually supplemented with commercially-produced multicomponent fortifiers (HMF): nonetheless, HM fortification such that intake really meets requirements is difficult, because HM protein and fat content is highly variable among mothers, gestational age at delivery, number of weeks after delivery, and time of day. To our knowledge, no previous studies have evaluated the influence of human milk nutritional and chemical features, and neither the effect of fortification, on gastroesophageal reflux (GER), which is common in preterm infants. The aim of our study was to evaluate whether the features of HM before and after fortification affect the pattern of gastroesophageal reflux in symptomatic preterm infants. In particular, fat and nitrogen content and osmolarity of HM were correlated with GER features. Methods. We studied seventeen preterm infants with symptoms suggestive of GER (frequent regurgitations and/or post-prandial desaturations). Each patient underwent a twenty-four-hour, continuous and simultaneous measurement of intra-esophageal impedance and pH by Multichannel intraluminal impedance and pH monitoring (Sandhill Scientific). During the study period, seven meals were given: the first one was always of unfortified HM, to avoid a potential carry over effect due to the features of previous feeding. The other six were divided into three couples (two meals of unfortified HM, two meals ofHM+ FM85 Nestlé 3% [Vevey, Switzerland], and two meals ofHM+ FM85 Nestlé 5%). The order of the three couples of meals was randomly assigned. Mother milk’s fat and nitrogen content was analysed by a Near Infrared Reflectance Analysis (NIRA). Furthermore, the osmolarity of each mother’s milk was tested. Results. An inverse correlationwas found between human milk protein content and the main reflux indexes, especially the acid ones, measured after the two HM meals. No correlation was found between fat content and any reflux index, neither between human milk’s fat and protein content. No correlationwas found between osmolarity values and GER indexes.We further analysed whether HM composition continued to be related to the pattern of GER also after fortification: we found that the correlation between HM protein content and the main GER indexes detected after fortification tended to reverse.We calculated the difference between RIpH detected after HM+HMF3% and the one detected before fortification (RIpH 3%), and also the difference between RIpH detected after HM+HMF5% and the one detected before fortification ( RIpH 5%): these indexes showed a significant direct correlation with HM protein content. In other words, patients who had a lowprotein content of naïveHMshowed a reduction of GER indexes after fortification. On the contrary, patients who had a high protein content of naïve HMshowed an increase of GER indexes after fortification. Conclusions. The evaluation of nutritional content of pretermHMmay allowa more precise and individualised fortification regimen, and thus improve nutritional management of preterm infants with gastroesophageal reflux.