Effect of infant stimulation on the adaptation to birth: a randomized trial*

Objective: to measure the effect of an infant stimulation therapy (auditory, tactile, visual and vestibular) on the adaptation to postnatal life of the mother-child dyad. Method: an experimental and blind study composed of 120 dyads of first-time mothers and full-term newborns, who practiced breastfeeding. The follow-up was conducted during the first five weeks of life and the evaluation was carried at two different times. Results: the adaptive capacity was measured in two modes. The physiological adaptive mode (activity and exercise and neonatal nutrition) and the interdependence adaptive mode (appropriate affection and proper development); and statistically significant differences were found in favor of the experimental group. Regression models that show the collaborative relationship between mother and child, and their reciprocity in the process of adaptation were proposed. Conclusion: the early stimulation is a therapy with bidirectional effect, because it has favorable effects on the person who administers it; promotes health and prevents illness in the process of adaptation to birth; especially in contexts of vulnerability. It is recommended its teaching to mothers and its application in the home environment. This study was registered in the Australian New Zealand Clinical Trial Registry (ANZCTR) under protocol number: ACTRN12617000449336.


Introduction
During pregnancy, the mother-child dyad begins, which is united through a symbiotic relationship in which the fetus takes from its mother what is necessary to grow and develop. After birth, the dyad changes its way of relating. This significant moment in the life of human beings is full of changes, which transform their way of interacting (1) . Mother and child face the challenge of understanding each other, and their relationship must be synchronous, since his well-being depends on her (2) .  (3) . The newborn tests the functioning of its organs and systems, faces the challenge of feeding himself and maintaining the metabolic and hydration balance. This is a fundamental skill that will be further improved as the days go by, but if the initial difficulty is maintained, its health and growth may be adversely impacted (4)(5)(6) .
Emotional adjustments in the newborn are manifested with a high level of stress (1) . A systematic review that included 15 studies of very good methodological quality evaluated the physiological and behavioral signs that newborns have in response to nociceptive stimuli associated with stress (7) . This review concluded that the responses are associated with the gestational age and are fundamentally changes in the heart rate and oxygen saturation, facial expressions, such as frowning, squeezing the eyes shut and marking the nasolabial sulcus, crying, among other signs (8) . The mother experiences a high level of anxiety, stress related to the new role, emotional sensitivity and depressive symptoms (9)(10) . Behavioral adjustments are characterized by a lack of maternal skills, which increases when it is first-time mother or when the delivery is performed through a cesarean section (11) . In turn, the newborn does not know many of the environmental stimuli, so during the first days of life it has difficulty to maintain a waking state that allows it to interact with its environment, and it is not able to maintain a state of calm alertness easily, what makes the process of feeding it even more difficult (12) . The greater the difficulty of the dyad in adapting, the greater the risk of postpartum depression (PPD) (3,10) . PPD makes the mother-child interaction difficult and causes delays in child growth and development (3,(10)(11)13) .
Therefore, support strategies such as home visits are of great importance. These strategies are provided in different health systems with the aim of preventing habitual complications and hospital readmissions.
However, developing countries such as Colombia do not provide comprehensive coverage and follow-up during this process, which is considered a highly sensitive period, and in which there is an increased risk of illness or death of the mother-child dyad (14) . These findings worry the nursing professionals, as it requires low-cost strategies that promote health and prevent diseases in this important period. Different studies show the positive effects of the early auditory, tactile, visual and vestibular stimulation therapy (ATVV), mainly in hospitalized premature newborns and their families (15)(16)(17) . In addition, it is presented as potentially effective when applied in the home context to benefit the process of adapting to postnatal life, since it allows the organization of the newborn behavior, which is expressed as the effective sucking ability, and that requires the hierarchical integration of social interaction systems: sensorial, autonomous, motor and behavioral (15) . It promotes growth (16)(17) and the emotional adjustments of the mother (17) . In this way, it is expected that the beneficial effects promote a favorable adaptation of the physiological adaptive mode (nutrition and activity and rest) and the interdependence adaptive mode (appropriate affection and proper development) of the mother-child dyads. If the newborn organizes its behavior sooner, its signals will be clearer and the relationship with its mother will be more synchronous. The effective sucking allows longer periods of neonatal sleep, contributing to the mother's rest and the prevention of emotional problems (18) . The objective of this study was to measure the effect of the early stimulation therapy ATVV on the adaptation to postnatal life of the mother-child dyad. The adaptation was measured through the physiological adaptive  Figure 1 shows the articulation between the concepts or outcome variables and the instruments used in the measurement in this study. All the instruments used were tested for their validity and reliability.

Results
The fieldwork was carried out from July 19 to November 27, 2016, at a Hospital in the city of Bogotá, D.C., Colombia. Taking into account the loss of participants, a larger number of participants was approached. However, despite the efforts undertaken, it was not possible to count on the estimated sample size at the end of the follow-up. Figure 2 shows the flow chart.
The greatest damages were observed in those mothers who underwent cesarean section, since mobility restriction in the days after delivery was a recurrent cause of their nonattendance at the evaluation meetings.   Table 3.
These characteristics allow us to select the previous regression model and qualify it as a good model to explain the risk of stress related to maternal role using 3 independent variables. It is concluded that, the older the mother, the lower the risk of stress related to maternal role (OR: 0.890, p: 0.034).
In addition, the use of a nursing bottle to feed the Based on Roy's adaptation model, it is confirmed that the mother-child dyad is an Integrated System, which cannot be interpreted in isolation, since the conditions that affect one also affect the other, so its adaptation must be understood jointly.

Discussion
Despite the efforts of the researchers to carry out the follow-up of the mother-child dyads, there was a large loss of participants during this study. Living conditions that are typical in a country in conflict, such as internal displacement and insecurity, which makes it difficult to use other forms of follow-up, such as home follow-up. It is possible that these findings are due to the pain and mobility limitations of mothers in using public transport during this short period, as well as the cultural practice of moving to the maternal home for quarantine care, even when it is necessary to move to another city. In view of the results in the Physiological Adaptive Mode, this study supports the results previously found by authors from Korea (17) and Colombia (23)  negatively affect the production of breast milk (26)(27) , and indirectly affect the amount of milk that the newborn can to suck. When this process does not take place in a harmonious way, mothers make use of bottle feeding and breast milk substitutes (28) . Therefore, the evidence shows that there is a negative relationship Rev. Latino-Am. Enfermagem 2019;27:e3176.
provision. In the same way, they thank the Hospital staff, who showed a positive attitude and offered their collaboration during the data collection stage.