Posted by: Indonesian Children | April 23, 2009

Development of Feeding and Swallowing Skills

Prenatal Swallowing and Sucking

In utero studies of fetuses have documented the early development of swallowing and oral-motor function3 (Table 1). In utero swallowing is important for the regulation of amniotic fluid volume and composition, recirculation of solutes from the fetal environment, and the maturation of the fetal gastrointestinal tract.4 The pharyngeal swallow, one of the first motor responses in the pharynx, has been observed between 10 and 12 weeks’ gestation.5 Recent studies have demonstrated swallowing in most fetuses by 15 weeks’ gestation and consistent swallowing by 22 to 24 weeks’ gestation.3

 

Table 1 – Gestational ages for swallowing and sucking

 

Swallowing function

Gestational age (weeks)

Pharyngeal swallow

10–14

True suckling

18–24

Tongue cupping

28

Sustain nutrition totally orally

34–37

 

True suckling begins around the 18th to 24th week and is characterized by a distinct backward and forward movement of the tongue. The frequency of suckling motions can be altered by taste. Taste buds are evident at 7 weeks’ gestation. By 12 weeks’ gestation, distinctively mature receptors are noted. Self oral-facial stimulation usually precedes suckling and swallowing. Tongue cupping is seen by 28 weeks’ gestation.

This backward and forward movement of the tongue in suckling is all that can be expected because the tongue fills the oral cavity at this stage of development. Backward movement appears more pronounced than forward movement. Tongue protrusion does not extend beyond the border of the lips. Serial ultrasound images have shown that suckling motions increase in frequency in the later months of fetal life.3 By 34 weeks’ gestation, a healthy preterm infant likely suckles and swallows well enough to sustain nutrition strictly through oral feedings. Some healthy preterm infants may be ready to begin oral feeding by 32 to 33 weeks’ gestation.

It has been estimated that the near-term human fetus swallows 500 to 1000 mL/day of amniotic fluid.4 Earlier reports had indicated that the fetus swallows about 450 to 500 mL of amniotic fluid per day (of the total 850 mL) and excretes about the same amount in urine.6 Decreased rates of fetal suckling are associated with digestive tract obstruction or neurologic damage. Intrauterine growth retardation may be a manifestation of neurologic damage. Lack of regular swallowing by the fetus should lead one to suspect problems that may be related primarily to the preterm infant or primarily to the mother. Maternal polyhydramnios characterized by excessive amniotic fluid in the uterus may result from multiple fetal and maternal etiologies. Severe polyhydramnios is more strongly associated with congenital malformations than mild or moderate polyhydramnios.7

Infant Feeding and Swallowing

Oral feeding that requires suckling, swallowing, and breathing coordination is the most complex sensorimotor process the newborn infant undertakes. Premature infant patterns differ from those of full-term infants. Five primary developmental stages of sucking characterized the maturational process (Table 2).8 Sucking patterns in infants born at less than 30 weeks’ gestation were monitored from the time they were introduced to oral feeding until they reached full oral feeding. The five-stage scale demonstrates the relationship between the development of sucking and oral feeding performance in preterm infants. A high interobserver reliability was observed on 50 bottle-feeding assessments. The authors suggest that there is no significant in utero maturation of sucking occurring between 26 and 29 weeks’ gestation, or they had insufficient statistical power to detect a difference over this developmental period. A significant correlation between the level of maturity of an infant’s sucking and gestational age was found. Feeding performance correlated with progression of oral feeding. These authors suggest that developmental scales can be used clinically for the identification and characterization of the oral sensorimotor skills of preterm infants at any point in their development as they progress in their individual oral feeding schedule. Objective and quantitative evaluations of infants’ nonnutritive and nutritive sucking would be helpful in evaluating strength and coordination. One proposal includes a finger pressure device to allow for quantification of specific measures of nonnutritive sucking in combination with a nipple/bottle system developed for monitoring nutritive sucking.9 However, there is no standardized quantifiable procedure available currently.


Table 2 – Five primary stages of sucking in preterm infants



Stage

Description

Source: Adapted from Lau et al.8

1a

No suction; arrhythmic expression

1b

Arrhythmic alternation of suction and expression

2a

No suction; rhythmic expression

2b

Arrhythmic alternation of suction and expression; sucking bursts noted

3a

No suction; rhythmic expression

3b

Rhythmic suction and expression; suction amplitude increases, wide amplitude range, prolonged sucking bursts

4

Rhythmic suction and expression; well-defined suction, amplitude range decreased

5

Rhythmic, well-defined suction and expression; increasing suction amplitude; sucking pattern similar to term infant

 

Term infants typically show food-seeking behavior through rooting for a breast or other nipple for bottle feeding. Preterm infants gradually achieve skills for rooting, suckling, and swallowing for functional oral feeding as they advance toward term. Important early developmental milestones and feeding skills from birth to 36 months are shown in Table 3. Children older than 36 months typically are eating regular table food and drinking from an open cup. They continue to refine their skills, but they do not attain new skills. Thus, this review focuses on feeding and swallowing in infants and young children.

Table 3 – Developmental milestones and feeding skills birth to 36 months

Age (months)

Development/posture

Feeding/oral sensorimotor

Source: Adapted from Arvedson and Brodsky10 (pp. 62–67).

Birth to 4–6

Neck and trunk with balanced flexor and extensor tone
Visual fixation and tracking
Learning to control body against gravity
Sitting with support near 6 months
Rolling over
Brings hands to mouth

Nipple feeding, breast, or bottle
Hand on bottle during feeding (2–4 months)
Maintains semiflexed posture during feeding
Promotion of infant–parent interaction

6–9 (transition feeding)

Sitting independently for short time
Self-oral stimulation (mouthing hands and toys)
Extended reach with pincer grasp
Visual interest in small objects
Object permanence
Stranger anxiety
Crawling on belly, creeping on all fours

Feeding more upright position
Spoon feeding for thin, smooth puree
Suckle pattern initially Suckle suck
Both hands to hold bottle
Finger feeding introduced
Vertical munching of easily dissolvable solids
Preference for parents to feed

9–12

Pulling to stand
Cruising along furniture
First steps by 12 months
Assisting with spoon; some become independent
Refining pincer grasp

Cup drinking
Eats lumpy, mashed food
Finger feeding for easily dissolvable solids
Chewing includes rotary jaw action

12–18

Refining all gross and fine motor skills
Walking independently
Climbing stairs
Running
Grasping and releasing with precision

Self-feeding: grasps spoon with whole hand
Holding cup with 2 hands
Drinking with 4–5 consecutive swallows
Holding and tipping bottle

>18–24

Improving equilibrium with refinement of upper extremity coordination.
Increasing attention and persistence in play activities
Parallel or imitative play
Independence from parents
Using tools

Swallowing with lip closure
Self-feeding predominates
Chewing broad range of food
Up–down tongue movements precise

24–36

Refining skills
Jumping in place
Pedaling tricycle
Using scissors

Circulatory jaw rotations
Chewing with lips closed
One-handed cup holding and open cup drinking with no spilling
Using fingers to fill spoon
Eating wide range of solid food
Total self-feeding, using fork

 

The development of independent, socially acceptable feeding processes begins at birth and progresses throughout the first few years of childhood. Oral sensorimotor skills improve within general neurodevelopment, acquisition of muscle control that includes posture and tone, cognition and language, and psychosocial skills (Table 3).10

Feeding and swallowing skill development parallels psychosocial milestones of homeostasis, attachment, and separation/individuation (Table 4).11 Infants during the first 2 to 3 months of life strive toward homeostasis with the environment. Goals include sleep regulation, regular feeding schedules, and awake states that are developmentally advantageous in the development of emotional attachment to primary caregivers. Successful pleasurable feeding experiences foster efficient nipple control, reaching, smiling, and social play. Thus, feeding gradually becomes a social event. Caregivers should not interpret pauses between sucking bursts as a need for burping or early satiety. Once caregivers interrupt feeding, some infants do not resume sucking readily. Caregivers then may perceive that an infant is full or too tired to continue, so they stop the feeding. If this pattern becomes habitual, the infant is likely to gain weight slowly or not at all, which results in undernutrition or failure to thrive. If the interactions between infant and caregiver fail to develop appropriately, the infant may indicate lack of pleasure, loss of appetite, and, in severe forms, vomiting and rumination. Significant feeding problems can evolve out of a mismatch between infants’ cues and caregivers’ interpretations of the cues.


Table 4 – Feeding-related psychosocial milestones: birth to 36 months



Stage

Psychosocial milestones

Source: Adapted from Chatoor et al.11

Birth to 3 months

Cues for feeding: arousal, cry, rooting, sucking

(homeostasis)

Caregiver responds to cues (leads to self-regulation)
Infant quiets to voice
Hunger–satiety pattern develops
Infant smile promotes interaction with primary caregiver
Pleasurable feeding experiences greater environmental interaction

3 to 6 months (attachment)

Primary interactions—”falling in love”
Reciprocity of positive infant and caregiver interactions
Consistent cues
Anticipation of feeding
Pauses likely socialization, not necessarily for burping or to indicate satiety
Smiling, laughing, social, alert
Preferred feeders are parents
Calls for attention by 6 months

6 to 36 months (Separation/individuation)

Responds to “no”
Imitates movements, and gradually imitation of speech
Play activity to explore environment (7–9 months)
Facial expression used to indicate likes and dislikes
Follows simple directions
Self-feeding emerges
Mealtimes become more predictable
Speech becomes important
Direction following—gradually 2–3 step commands
Mealtimes become part of whole family schedule
Rapid increase in language 24–36 months
Independent feeding by end of period

 

Transition Feeding

Infants show readiness for the transitional feeding period that usually begins around 4 to 6 months in typically developing infants, which also is the period of attachment for psychosocial milestones (Table 4).11 Transition feeding describes the readiness for and initiation of spoon feeding, usually with thin cereal mixed into breast milk or formula for most infants. Infant developmental skills that indicate readiness for spoon feeding include, but are not limited to, upright sitting with minimal support, midline head position maintained for several minutes without support, hand to mouth motor skills, dissociation of lip and tongue motions, and anatomic changes resulting in more space for the tongue within the oral cavity that allow for vertical motion of the tongue in addition to the previously restricted movements of “in and out” suckling. Over the next several months, infants gain oral sensorimotor skills for accepting thicker and lumpier food by spoon. Then, they move into a period of greater independence noted by finger feeding of easily dissolvable solid food. They gradually become more precise in picking up small pieces of food (or other objects), as they attain a pincer grasp with thumb and forefinger, which is expected by 10 to 12 months.

Critical and Sensitive Periods with Implications for Behavioral and Sensory-Based Feeding Problems

The concept of critical and sensitive time periods in overall human development is well documented in some areas of development and in animal research. Lorenz12 interpreted findings from animal embryologic studies to imply that there is a period during early development when the organism is primed to receive and perhaps permanently encode important environmental information. These interpretations do not mean that later learning cannot occur or that it is not important, but they do emphasize the possible significance of these early experiences.

Critical and sensitive periods are believed to exist in the development of normal feeding behavior. Descriptions of these critical periods typically focus on the introduction of chewable textures (Table 3). Children develop oral side preferences for chewing that relate to hand preferences in many instances. Chewing skills vary with textures. Children develop mature chewing skills for solid foods earlier than for viscous and pureed foods. However, it is common for children who have not mastered the timing and coordination for swallowing purees and other smooth food to be kept on those textures because caregivers may believe that these children are not ready for introduction of chewable food, which is not necessarily true. Children need to be introduced to solid foods at the most appropriate times. Children may reject solids upon initial presentation if they are introduced after the critical periods. The longer the delay in the introduction of solids, the more difficult it is for many children to accept chewable food. Withholding solids at a time when a child should be able to chew (6 to 7 months developmental level) can result in food refusal and even vomiting,13 which in turn may have a significant negative effect on nutrition and hydration status.

Studies in mice reveal that those fed a soft-feed (powdered) diet after weaning reduced synaptic formation in the cerebral cortex and impaired the ability of spatial learning (radial maze) in adulthood when compared with mice fed a hard-feed (pelleted) diet.14 Similar deficits may result from lack of experience and exposure to age-appropriate foods in humans, providing a conceptual framework to explain clinical observations of the challenges encountered in the learning of oral sensorimotor and other skills in children not fed during critical/sensitive periods for oral skill development. Perhaps when children have not been introduced to solid foods within the critical sensitive periods, broad aspects of development may be affected negatively. One may assume that these children missed not only this critical period for chewing, but also the underlying skills, which include trunk stability, head control, mobility of limbs, and mouthing experiences involving hands, fingers, and toys. Physiologic processes that are underpinnings for oral sensorimotor and swallowing skills, such as respiratory control, also have critical periods that can impact the feeding process.

Psychosocial development, personality, and environment are additional factors that must be considered for children with feeding issues. Some children may respond in aversive ways when presented with certain textures, tastes, or temperatures of food and liquid. These same children may be hypersensitive to tight clothes or tags on their clothes. They may not like to wear shoes. They may get upset when their hands get dirty, so they refuse to do finger painting and will not put their fingers into pudding or other pureed food.

Critical and sensitive periods may apply to the mother, with effects related to the potential for efficient feeding and global development of an infant.15 Maternal early contact with both preterm and term infants has been found to have a positive effect on the mother’s attachment behavior and ultimately enhanced development of the infant.

Effects When Oral Feeding Is Not Possible in the Newborn Period

When infants with major physical and physiologic problems are prevented from initiating oral feeding in the same time frames as their more typically developing peers, many demonstrate prolonged delays and significant difficulty with oral feeding. In addition, significant variations are found in the form and function of the ingestive systems of age-matched healthy infants and at-risk infants. Ultrasounds revealed that fetal swallowing occurred most commonly in the presence of oral-facial stimulation. Hands were touching face and mouth. In some instances, fingers or thumbs were seen in the mouth. Perhaps some infants miss critical periods while still in the womb. Miller and colleagues3 postulate that prenatal development indices of emerging aerodigestive skills may guide postnatal decisions for feeding readiness and, ultimately, advance the care of medically fragile neonates. Clinicians must have knowledge regarding normal development in order to appreciate and understand the implications of differences in infants and young children with feeding and swallowing problems, which are likely to be just one or two pieces of a much larger and more complex puzzle. All aspects must be delineated in order to plan management strategies that will permit adequate nutrition without pulmonary issues and without stress to the child as well as to the caregiver.

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Taste and Smell in Oral Feeding of Infants and Young Children

Understanding an infant’s awareness of taste and smell, along with responses to textures and temperature, is fundamental for clinicians of any discipline to determine the potential for acceptance of new foods. Physicians, dietitians, nurses, and therapists who guide parents when children are failing to thrive, or have limited range of foods in the diet, must examine the broad parameters that can impact on a child’s feeding status. These experiences occur much earlier than many professionals would expect. Initial experiences with flavors occur prior to birth, because the flavor of amniotic fluid changes as a function of the dietary choices of the mother. Flavors from the mother’s diet during pregnancy are transmitted to amniotic fluid, which are not only perceived by the fetus, but enhance the acceptance and enjoyment of that flavor in a food during weaning from the breast. The ability to detect additional tastes and flavors develops after birth. Thus, it is clear the early sensory experiences have an impact on the acceptance of flavors and foods during infancy and childhood.16

It has long been shown that human infants are born with a preference for sweet. Their sensory apparatus can detect sweet tastes. Tatzer and colleagues17 found that preterm infants fed exclusively via gastric tubes exhibited more nonnutritive sucking in response to minute amounts of glucose than to water solutions presented intraorally. Infants produced more frequent and stronger sucking responses when offered a sucrose-sweetened nipple compared with a latex nipple.18

Exposure to flavors in breast milk may serve to heighten preferences for these flavors and facilitate the weaning process. Some breast-fed infants are more willing to accept a novel vegetable upon first presentation than are formula-fed infants.19 Children who have been breast-fed for at least 6 months are also less likely to become picky eaters.20

The ability to detect and prefer a salt taste does not appear until infants are about 4 months of age. Animal model studies demonstrate that this developmental change may reflect postnatal maturation of central and peripheral mechanisms underlying salt taste perception.21 The preference that emerges at this age appears to be largely unlearned.

An example of the importance of early exposure to flavors is found in the acceptance of protein hydrolysate formulas by 7-month-old infants who had readily accepted this kind of formula when compared to their regular milk- or soy-based formula in the first couple months of life. These formulas are known by a variety of names depending on the company that produces and distributes them in the United States and in other countries throughout the world. A sensitive period in early infancy is suggested as at least one important factor, as shown by the finding that those infants 7 months and older avidly accept these formulas if they have experienced them during the first months of life. However, in marked contrast, 7- to 8-month-old infants who had no previous experience with hydrolysate formulas strongly rejected them and displayed extreme and immediate facial grimaces, similar to those observed in newborns in response to bitter and sour tastes.22

Professionals who make decisions regarding feeding of infants and young children have to consider multiple variables. Differences in flavor acceptance that occur from breast-fed to bottle-fed infants and that likely change over time reflect complex interactions of sensory and motor factors.

 

Reference

  1. Ross MG, Nyland MJM. Development of ingestive behavior. Am J Physiol 1998;43:R879–R893.
  2. Hill DL, Mistretta CM. Developmental neurobiology of salt taste sensation. Trends in Neurosci 1990:13:188–195. | ChemPort |
  3.    Mennella JA. Development of the chemical senses and the programming of flavor preference. Physiologic/immunologic responses to dietary nutrients: role of elemental and hydrolysate formulas in management of the pediatric patient. Report of the 107th Conference on Pediatric Research 9. Columbus, OH: Ross Products Division, Abbott Laboratories, 1998:201–208.
  4. Link DT, Rudolph CD. Gastroenterology and nutrition: feeding and swallowing. In: Rudolph CD, Rudolph AM, eds. Rudolph’s Pediatrics, 21st ed. New York: McGraw–Hill, 2003:1382.

 

 

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PICKY EATERS CLINIC

KLINIK KHUSUS KESULITAN MAKAN PADA ANAK

JL TAMAN BENDUNGAN ASAHAN 5 JAKARTA PUSAT, JAKARTA INDONESIA 10210

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https://mypickyeaters.wordpress.com/

 

Clinical and Editor in Chief :

DR WIDODO JUDARWANTO

email : judarwanto@gmail.com,

 

Copyright © 2009, Picky Eaters Clinic Information Education Network. All rights reserved.

 

 


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