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Introduction
Feeding behavior development occurs before birth and completes around 34-36 weeks. This pattern includes sucking, swallowing, and breathing [1]. Swallowing is the procedure of transferring food (bolus) from the mouth to the stomach [2]. Its disorders have several possible etiologies, such as neurological disorders, anatomical abnormalities, genetic conditions alone, or their combinations, all of which will lead to nutritional deficits [3]. Studies have shown that nearly 25%-40% of full-term infants and over 80% of early-term infants have some feeding or swallowing dysfunction, mostly colic, vomiting, slow feeding, or denial to eat [4, 5, 6]. Feeding and or swallowing difficulties usually subsides as the infant grows older. However, affected full-term infants (gestational age ≥37) who do not improve are at a greater risk of invasive infections such as aspirated pneumonia [4, 5, 6, 7]. The main consequence of feeding/swallowing disorders is malnutrition. 
There are several ways such as breast, bottle, syringe, tube feeding, and parenteral feeding to feed infants [7]. The skill to suck the nipple of the breast and or suck the tip of a bottle is part of the instincts of the infant [8]. As stated by a 2010 healthy people study, breastfeeding is the best method and should be line up over the other methods; it is vital for both the infant’s and the mother’s health [9, 10]. The first-week post-natal is the most important period for establishing a healthy breastfeeding routine. As both the mother and the infant are learning how to breastfeed, it is important that it is done correctly and that good habits are known at this stage [9, 11, 12]. If breastfeeding is not done correctly, insufficient milk transmission can cause infant weight loss, dehydration, and serious medical complications such as death [11, 13]. Furthermore, these problems can increase the length of hospitalization, which leads to increased nosocomial infections and potential disabilities, as well as additional financial costs that flare to the parents’ anxiety [14, 15, 16, 17]. 
Infants should have well-coordinated sucking, swallowing, and breathing skills [18, 19]. A normal sucking pattern is a constant burst of more than 10 sucks with momentary pauses in between; swallowing and inhalations continuously occur throughout a consecutive pattern [4, 8, 20]. In a prospective study Bingham et al. examined the nonnutritive sucking and feeding skills in premature infants. They found that infants with a correct sucking pattern achieved independent oral feeding 3 days earlier than infants with incorrect sucking patterns [21]. 
Treatment methods emphasize oral stimulation, non-nutritional sucking, and altering the infant’s position during feeding; these treatments should lead to a reduced time to independent oral feeding, increased milk transfer rate, increased weight, and reduced hospitalization time [22, 23, 24, 25, 26]. Overall, the main goal of every intervention is to help the infant reach age-appropriate nutritional milestones and to ensure safe swallowing. Several treatments have been studied on infants with feeding/swallowing problems.
Mahmoodi et al. studied the 5-minute premature infant oral motor intervention (PIOMI) to stimulate oral movements in premature infants. Infants who received 5-minute PIOMI demonstrated an earlier onset of oral feeding and reduced hospitalization compared to the control group [1]. In another study, Fucile et al. examined the impact of the 15-minute oral stimulation program on achieving full oral feedings in infants (old enough to tolerate 15 minutes of therapy), who showed substantial feeding improvements [22]. Lessen examined the effects of PIOMI on feeding skill development and the length of hospitalization in preterm infants. Infants who received PIOMI showed improved feeding efficiency, transitioned to full oral feedings earlier than the control group, and had lower hospital stays [15]. 
The 5-minute PIOMI and 15-minute oral stimulation program are similar in their physical steps. However, the latter has extra steps and takes 15 minutes. Arora et al. showed that the oral stimulation program improves oral motor skills and decreases the transition time from gavage to full independent feeds by mouth in preterm infants [27]. According to Barlow et al., the oral stimulation program significantly increased the proportion of oral nutrients in preterm infants [28]. 
According to our evaluation, a comprehensive study on the effectiveness of the different treatment techniques in full-term infants at 37 weeks who suffer from feeding/swallowing problems has not yet been done [4, 5]. The short nature of PIOMI has not yet been studied on full-term infants who are poor feeders. Therefore, this study aims to compare the effects of 5-minute PIOMI and the 15-minute oral stimulation program for breastfeeding achievement in full-term infants with feeding problems admitted to the neonatal intensive care units (NICUs).

Materials and Methods
Study design and participants 
The study was carried out on 51 full-term infants (26 girls and 25 boys) with a mean age of 37.90 weeks (range 37-39 weeks) at birth and 38.33 weeks (range: 37-41 weeks) at the beginning of the intervention in the NICU wards of Ghaem and Akbar hospitals in Mashhad City, Iran. All full-term infants who participated in this study had feeding/swallowing dysfunctions and difficulty sucking for any reason related to their underlying diseases (such as asphyxia, metabolic diseases, brain disorders, infections, etc.). All parents were thoroughly briefed on the study and gave written consent to study their infants. All infants demonstrated feeding/swallowing disorders, according to the early feeding skills (EFS) screening test [29]. None of the full-term infants have progressive diseases, congenital anomalies (cleft lip and palate), or chromosomal abnormalities. Subjects were excluded from the study if there was a risk of unmanageable harm to the infants and if the parents did not consent. Speech therapists (the first authors of this study) enrolled the participants and assigned them to the interventions.

Assessment techniques
Before and after treatment, the type of feeding method was assessed by a pediatrician, and the infant’s swallowing status was evaluated by a speech and language specialist using the EFS screening test [29].

Experimental design
The sample included full-term infants born between 37-39 weeks (mean=37.90) with feeding/swallowing disorders who were randomly assigned using a stratified blocked randomization method by a statistician into three groups of 17 infants each. Two treatment protocols were used to evaluate the effect on infant sucking and swallowing skills. Protocol “A” was the 5-minute PIOMI treatment, and protocol “B” was the 15-minute oral stimulation program. The first group received the “A” protocol, the second group received the “B” protocol, and the control group (group C) received routine care. All NICU personnel (physicians, nurses, etc.) were blinded to group assignment (except the study authors). The intervention was initiated at 37-41 weeks. Each treatment included 7 sessions, and all exercises were performed once a day (in the morning) by one person (the first author). It was stopped if the infants were medically unstable or had any episodes of oxygen desaturations, apnea, or bradycardia during the intervention. After the end of the treatment period, therapeutic advice was given to the parents of the infants in the control group, and routine hospital treatment was continued for all three groups. Infants participating in all three groups were monitored from entry into the study until their discharge from the hospital.

“A” protocol
The 5-minute PIOMI (Figure 1) was used in group A.

This program has demonstrated excellent intervention fidelity and is the standard of care for preterm infants as young as 29 weeks through early infancy [30]. The 5 minutes of therapy has 8 steps to increase motor-oral skills and coordination of sucking, swallowing, and breathing [30] (Table 1).

The infants were positioned supine in the isolate. The 5-minute PIOMI was performed for 7 consecutive days and followed by a post-treatment evaluation by the speech therapist using the EFS screening tool.

“B” protocol
The 15-minute oral stimulation program was used in group B. The 15-minute program is used for full-term infants who can tolerate a longer period of therapy than early-term infants [22] (Table 1). The infants were positioned supine in the isolate. These exercises were performed for 7 consecutive days and followed by a post-treatment evaluation by the SLP using the EFS screening tool.

Statistical analysis
All variables were described by descriptive statistics, including mean, median, standard deviation, minimum, and maximum for quantitative variables, as well as frequency and percentage for categorical variables. The normality of variables was assessed by the Shapiro-Wilk test. The homogeneity of the groups in terms of demographic variables was evaluated by the chi-square or Kruskal-Wallis test. The chi-square test using exact P values was used to check the differences between categorical variables across three groups or sub-groups. The within-group differences were evaluated through the marginal homogeneity test. The stratification was used to assess and control for confounding based on gender subgroups or strata. All statistical analysis was performed using R software, version 4.0.2, and the significance level was set at 0.05.

Results 
A total of 61 full-term infants were included in the study. Two infants were excluded from the study due to seizures, and 3 due to discontinuing treatment. In addition, 5 infants were excluded from the study due to parental dissatisfaction (Figure 2).

In total, 51 term infants completed the study. Table 2 compares age (at birth and the start of 5-minute PIOMI or 15-minute oral stimulation program), sex, and feeding methods before treatment in the three groups. As mentioned previously, age at birth and the beginning of the intervention and feeding method was comparable between the 3 groups (P>0.05). At the same time, the frequency of male infants was significantly lower in the 15-minute oral stimulation program group (P=0.034).

Based on the results of the marginal homogeneity test in Table 3, before the intervention, none of the infant groups were breastfed, whereas this changed to 17.6%, 41.2%, and 5.9% in the 5-minute PIOMI, 15-minute oral stimulation program, and control groups, respectively (P<0.05).

Table 4 shows that the 15-minute oral stimulation program group had shown significant improvement in feeding compared to the 5-minute PIOMI and control groups (P=0.007).

As the sex distribution was different between the 3 groups, we stratified the analysis based on gender as one way of controlling confounding effects. According to the exact P of the chi-square test, there was no significant difference between the three groups in terms of post-intervention feeding methods in females (P=0.290). But for males, breastfeeding frequency was significantly higher in the 15-minute oral stimulation program group (P=0.03) (Table 5).

Discussion
This study was conducted to identify the effects of various treatment methods on term infants and compare the duration of the lactation therapy between PIOMI and the 15-minute oral stimulation program. We found that the 15-minute oral stimulation group had better feeding effects on infants than the 5-minute PIOMI and the control groups. Those receiving longer treatment (15-minute oral stimulation group) had a greater improvement than those receiving shorter treatment (5-miute PIOMI group). However, the control group showed minimal improvement in feeding methods, most likely due to the normal growth and development over the 7 days (Table 3). Due to the age of the participants in this study, the 15-minute therapy period could be performed. The group using the longer 15-minute therapy had a greater positive impact than the PIOMI group, signifying that longer treatment yields better results. 
This finding is in line with the study of Osman in 2016, where PIOMI was provided to two groups at 30-32 weeks; one group received 7-day therapy, and the other received a longer treatment period. They found that the additional days of therapy led to a greater impact on their feeding skills [31]. Fucile et al.’s findings showed the positive effects of the 15-minute oral stimulation program on the attainment of full oral feedings in infants [22]. Furthermore, Thakker et al. studied PIOMI on preterm infants with a mean age of 32 weeks, and due to their age, they could offer PIOMI two times per day rather than 1 time. They found considerably improved feeding compared to the control group [32]. 
According to the findings of Lessen Knoll et al., an early start to therapy with PIOMI on preterm infants at 33 weeks enhanced feeding skills over time compared to the control, who only had negligible improvements due to normal development [33]. Oral feeding is a crucial milestone for appropriate growth and development [34, 35, 36]. This finding is consistent with Coker-Bolt et al.’s study, which found that oral motor stimulation was effective in infants. In this study, the treatment group received the oral motor treatment once a day, 6 days a week, and attained full bottle feeding 2 days earlier than infants in the control group [37].
In line with our research, a systematic review study by Tian et al. involved 11 clinical trials and concluded that oral motor intervention might improve feeding skills. Furthermore, they found that intervention decreased duration of hospitalization and family anxiety [38]. Assadollahpour et al. reported that non-nutritional sucking and oral stimulation treatments improved the feeding skills of infants which was in line with the results of the present study [39]. Green et al. distributed a Cochrane review on several oral motor stimulation techniques, including PIOMI, and found that oral stimulation in preterm infants improved infant feeding skills [40].
It is important to note that in the current study, a bias was found due to the sex distribution differences in the participants; the 15-minute oral stimulation program group had significantly more females than males, and the PIOMI group had significantly more males. However, this bias was considered in the statistical analysis. This limitation advocates further studies be undertaken with larger groups of different sexes and ages. The influence of these variables will be essential for future evaluations. We also recommend that more research be done on this topic by comparing other treatment methods for infant feeding problems. The validity of oral motor therapy has been shown through its analysis in different environmental settings in several countries worldwide.

Conclusion 
The 5-minute PIOMI has been confirmed as an effective early intervention for small preterm infants as young as 29 weeks, and the short 5-minute therapy time is accepted in the preterm infant population. It influences the brain’s plasticity and improves neurosensory and motor skill development for feeding. The current study indicates that PIOMI remains effective versus the control group in the full-term population as well, though the longer 15-minute oral stimulation program, while being similar, is more effective in term infants. This finding shows that full-term infants can endure and benefit from longer than 5 minutes exercises per day of oral motor therapy. 

Strong points of our study
The strengths of the current study are the validation that the short ـــand the longer 15-minute treatment protocols effectively increase feeding efficiency in full-term infants and the supporting previous study findings that the longer the therapy would have better outcomes. For the term infants, this would show the benefit of doing a longer therapy period each day. For the preterm population, where only shorter therapy can be tolerated, it would indicate to start treatment sooner and continue it for more days and or more times per day for the greatest effect.

Data availability statement
All data generated or analyzed during this study are included in this article and its supplementary files. Further inquiries can be directed to the corresponding author.

Ethical Considerations
Compliance with ethical guidelines
All participants had given their written consent to participate in the study, and the data collection procedure was approved by the Ethics Committee of Mashhad University of Medical Sciences (Code: IR.MUMS.REC.1399.473).

Funding
This research was supported by Mashhad University of Medical Sciences.

Authors' contributions
All authors equally contributed to preparing this article.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
We acknowledge the support of the Paramedical Faculty of Mashhad University of Medical Sciences, who helped us to carry out this study and improved the quality of this research.


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