Existing controversies around the topic of the most adequate way of feeding for the term newborn could be resolved in a simple manner based on the growing body of scientific evidence supporting human lactation, a physiological practice in humans, the rule in all mammals. To ignore or circumvent this practice leads pediatricians and other health professionals to confront this option with a variety of alternatives characterized by altering the physiology of the newborn as well as the relationship with the mother.
Breastfeeding culminates a series of physiological processes in the maternal organism as well as in the newborn child, which are meant to allow and facilitate this form of feeding. These processes are facilitated by diverse reflexes present in the mother and neonate. As part of the process of labor, oxytocin secretion by the hypothalamus and its release from the pituitary gland help to maintain uterine contraction during labor and childbirth.1 When cervical dilation is completed, there is a peak release of oxytocin (Ferguson-Harris reflex) that helps to regulate and maintain uterine contractions in order to complete labor and the subsequent birth, a time at which the highest concentration of this hormone is reached.2 When the placenta is detached, estrogen and progesterone levels decrease. Concentration of prolactin increases, a hormone that stimulates milk secretion by the alveoli of the mammary gland. Oxytocin also stimulates the milk ejection reflex, which is triggered by the infant’s sucking and favors lactation.3 The feedback process between the infant’s sucking and stimulation of milk production by the mother’s breast starts with the first act of breastfeeding in which the newborn receives maternal immunoglobulin-rich colostrum. Initiation of the breastfeeding episode stimulates the secretion of prolactin, reaching its peak 20 to 40 min later. When the episode is prolonged by 20 to 30 min, prolactin plasma level is maintained elevated for up to 3 to 4 h.
During breastfeeding, a series of reflexes, mostly mature at birth, are placed into practice. First, the search reflex is exercised, triggered by the proximity of the nipple to the commissure of the mouth. Stimulation from the newborn’s lips and tongue on the areola provokes the erection reflex of the mother’s nipple, which facilitates its identification by the newborn. Once the nipple is localized, the sucking mechanism takes effect, which includes positioning the tip of the tongue behind the lower lip and the lower gums to take in the nipple in the mouth. Next, the tongue channels itself around the areola and the lower jaw moves upwards, pushing the tongue that rests on it towards the palate. This movement is accompanied by the ejection of milk from the mammary tissue in response to oxytocin. Compression of the tip of the nipple between the newborn’s tongue and the palate is followed by movement of the tongue, which rises on the anterior portion at the same time that the posterior part depresses itself, with which milk is displaced towards the pharynx and swallowing can begin. The sucking pattern is characterized by two suctions/second followed by one to four swallows per series, which carry the milk content towards the esophagus, prompting the waves of propulsion that move the swallowed milk towards the stomach. The swallowing mechanism is present from intrauterine life and is completely functional at birth. It is important to mention that during lactation, the tip of the nipple does not surpass the posterior third of the newborn’s tongue. The strength of the suction of the newborn as well as the frequency of breastfeeding establishes the periodicity and quantity of prolactin secreted by the maternal organism.
Other aspects associated with mother’s milk production secondary to nutrition but important for newborn development include the visual and physical contact that is necessarily established between the mother and the newborn during breastfeeding. It is true that visual contact with the newborn can also be established during bottle feeding; however, physical contact is often limited in this situation, especially when the feeding is offered not by the mother but by a nurse. As we have understood the implications associated with maternal breastfeeding, which can be short term (lower risk of gastrointestinal and respiratory infections)4 and long term (lower risk of obesity and diseases such as metabolic syndrome, diabetes and cardiovascular disease),5-7 it is also necessary to understand the repercussions that physical contact with the mother may have such as visual stimulation, identification of odors associated with breastfeeding and sounds and textures resulting from the act of maternal lactation on the neuronal, psychological and congenital development of the newborn.
The dilemma that Jiménez-García et al. sought to clarify in the article published in this issue of of Boletín Médico del Hospital Infantil de México only presents itself if any of the reasons for choosing supplementary infant formula present themselves from the time of birth, which include, as cited by the authors, maternal fatigue and time of birth, among other reasons. This leads the pediatrician to choose how to offer supplementary nutrition to the newborn at the initiation of extrauterine life.8 Starting from the observation that “unlike breastfeeding, it seems that with bottle feeding the phenomenon of intake self-regulation does not appear to take place,”9 the decision analyzed by these authors revolves around how to adjust the volume of the formula offered to the newborn in a bottle with a nipple in order that the volume ingested does not exceed the gastric capacity. It is also sought to take into account the physiological changes that occur at this stage of transition that involves enormous changes for the newborn. As background for their study, the authors present the arguments stipulated in guidelines published in Mexico that note an intake of 70-80 ml/kg of weight at birth, with 10-ml daily increases until the seventh day of life.10
To achieve this intake, Jiménez-García et al. present the pro and con arguments for the two feeding modalities studied. The first, feeding on demand, seeks to emulate the self-regulation that is established when the newborn receives his/her nourishment from the breast. This is strongly interrelated with the volume secreted by the mother’s mammary gland beginning with the initial secretion of colostrum, followed subsequently by early milk and, finally, mature milk, which is stimulated by the strength of the suction and the frequency of the feedings. The second method proposes intake of pre-established volumes of formula based on the expected gastric capacity of the newborn, estimated according to body weight (weight in grams –3/10).
The approaches proposed by Jiménez-García et al. when comparing these two feeding regimes for the term, eutrophic newborn (delivered vaginally or by cesarean section) are current, relevant and balanced. The research design chosen was the follow-up of two groups of newborns who received formula on demand or in volumes calculated according to the newborn’s gastric capacity and according to the clinical judgment of the treating physician. It is noteworthy that the allocation was not random and that the intervening elements in the decision of the attending physician were not defined and would provide better understanding and evaluation of the methodology. The commercial formula used to initiate feeding from the third hour of life was the same in both groups of newborns, and the bottle was offered by the nursing personnel trained in the feeding technique. It is mentioned that, in the absence of an absolute contraindication, mothers were allowed to attempt to breastfeed the child. However, it is not specified in how many cases this occurred, although it can be assumed that it was not achieved in any of the cases because then it would not have been possible to carry out the comparisons between the volumes of milk consumed by the newborns under study. Clinical measures of monitoring and follow-up on the acceptance of the formula, measurement of the volumes ingested and possible complications or secondary events to the feedings such as abdominal distention, regurgitation or vomiting were carefully defined and executed. Similarly, the provisions taken related with the possible presentation of clinical events such as hypoglycemia, convulsions or enteral complications were carefully identified and monitored so that in case they were present, appropriate care could be offered. There was no complication in any of the cases that would have required prolonged hospitalization of the newborn, and all children were discharged between 24 and 48 h after birth. Statistical management of the data collected was well described and satisfactorily carried out as expressed in the tables and figures presented. Based on their results, the authors identified that the better option for feeding newborns who met the inclusion criteria corresponded to the one based on calculating the newborn’s gastric capacity. This modality was associated with greater regulation on the volume offered during each feeding and less frequency of vomiting. Although not alarming from the clinical point of view, vomiting is often a sign of alarm to parents, and a motive of anxiety. Also, restricted feeding based on estimated gastric capacity of the newborn was accompanied by less abdominal distention. It is important to note that neither of the two feeding modalities studied was negatively associated with weight loss commonly seen during the early postnatal period that. As the authors note, this may be 4% of body weight in the first 72 h of life. One must not lose sight of the fact that there was a need to interrupt the protocol (violation to the indication of the choice of feeding modality) in the group receiving formula according to the calculation of gastric capacity, following the clinical judgment of the attending physician or nurse responsible for monitoring feeding. In particular, there was greater presence of vomiting with feedings greater than the calculated gastric capacity.
It should be recognized that the authors identified different limitations in their study, notable among which was the absence of a group that would have been bottle or glass fed, but with mothers’ milk instead of formula. The unique composition of maternal milk could influence the time of gastric emptying as well as other aspects indicative of greater tolerance. Also notable was the relatively short follow-up period (24 h). This was in accordance with the characteristics of the population studied and the ethical aspects related with unnecessary retention of mothers and newborns in hospitals in the absence of a medical indication.
One further aspect that the authors did not approach was the possibility that any of these modalities may have been followed by the adoption of breastfeeding after the mother/child discharge from the hospital. Of course, there are many other factors that may be influential, from social aspects (such as the relationship of the mother and father of the newborn, social support for the mother, occupational situation of the mother) to demographic aspects (age of the mother, parity), economic (need to integrate into the work environment, family situation), education (mother’s knowledge about the advantages of breastfeeding), medical (medical indications that contraindicate breastfeeding such as the case where the mother receives medication that is released into the breast milk and may be potentially harmful to the newborn), etc. Even so, the prevailing situation in Mexico and in other low and medium income countries related with the discontinuation of exclusive breastfeeding as the best way of providing nourishment to the child during the first 6 months of life is frankly alarming.11 The role played by the physician, obstetrician, pediatrician, family doctor, internist, and nursing personnel in supporting–or not–breastfeeding is determinant.
In conclusion, the study by Jiménez-García et al. offers an objective, clear and balanced view on the aspects that could guide the pediatrician to evaluate the way in which the newborn is offered artificial milk formula, particularly when the pediatrician has the responsibility to supervise its use when offered in a bottle. It is a good example of the care that the medical personnel should maintain in order that the newborn can receive sufficient, adequate and safe intake of formula, ensuring the infant’s discharge from the hospital in the best possible clinical condition. The importance of the promotion of adopting early and well-oriented breastfeeding cannot be overly emphasized. It should be noted that even when breastfeeding is not started immediately after birth, as recommended, it is perfectly feasible for it to be established in a satisfactory and lasting manner when begun in the first days of life of the newborn.
Homero Martínez Salgado
Investigador Titular en Ciencias Médicas “F”,
Hospital Infantil de México Federico Gómez,
Mexico City, Mexico
E-mail: homero@rand.org