Nurturing is the process by which infants survive, grow and develop. It has emotional, cognitive and nutritional aspects. It takes place within a dyadic relationship made up of the infant and its principal caregiver [10].

In a well-functioning dyad, mother and infant interact in a reciprocal manner so that the infant’s behavior and the caregiver’s behavior are mutually regulatory [11]. Actions, responses, and reactions occur during which the infant’s cues are appreciated by the mother who then reacts in a timely, sensitive, contingent manner [12]. These interactions, over time, foster the infant’s sense of existing as an individual, physically and cognitively separate from his or her mother, and able to express a need with the expectation that it will be correctly interpreted and responded to. In order for a dyadic relationship to function, the mother must have first “fallen in love” with her infant and “claim” her baby as her own, physically and emotionally [13]. “Claiming” may occur immediately in the delivery room the moment the baby is put to her breast, it may occur sometime later, or may not sufficiently take place at all. Without it, however, there may be insufficient motivation for devoted caring and the capacity for feeling pleasure and pride in her baby and in her achievements as a mother, all of which foster effective nurturing [14].

The infant’s capacity to engage in dyadic interaction depends upon its ability to manage transitions of state, including those required for feeding and eating. The infant in utero has little experience with changes in state. Feeding is continuous; there is no experience of hunger or thirst. The fetus experiences periods of sleep and wakefulness, but, unlike sleep and wakefulness in post-natal life, it does not occur in a changing environment, nor does it have much effect upon its environment. The intra-uterine environment presents fewer stimuli for arousal and quiescence or changes in state.

Once out of the womb, however, the infant is inundated by an environment that changes continuously. The ability of an infant to make transitions from one state to another (e.g., hunger/thirst, followed by feeding, followed by satiety) depends upon, for example, the infant’s temperament as well as the commitment, sensitivity, and skill of the mother.

Nutritional adequacy is comprised of a sequence of phenomena: (1) Adequate food must be available in the environment. (2) The child must take in adequate amounts of food. If food is not offered, older children can forage, but infants and toddlers depend entirely on their caregivers’ recognition of, and responses to their hunger signals. The dyadic relationship, of which feeding and eating is a major part, must work well enough to avoid feeding disorders that impair parents’ ability to feed and their infant’s ability to eat in a comfortable, satisfying manner. (3) Sufficient food must be retained and not regurgitated or vomited before it can be digested. (4) The food must be digested before it can be absorbed. A child with cystic fibrosis, for example, may grow poorly, even though he may eat more than normal amounts of food, because the pancreas fails to secrete enough enzymes to digest the food that enters her intestine. (5) The lining of the small intestine is the surface through which the products of digestion enter the bloodstream. If the area of this absorptive surface is reduced, as in celiac disease, weight gain and linear growth may be severely impaired. (6) As soon as the products of digestion have been absorbed, they may be utilized for growth. The presence of sufficient nutrients in the bloodstream promotes normal growth. However, severe physical and/or emotional stress can interfere with tissue-building and promote tissue wasting so that the nutrients available for incorporation into growing tissues are, instead, lost through the urine along with the waste products of normal metabolism.

This sequence of phenomena essential for growth is depicted in Table 7.1.

Irene Chatoor described six feeding disorders of infancy and early childhood [15], three of which are often associated with FTT: Feeding Disorder of State Regulation (onset during the first 2 months); Feeding Disorder of Reciprocity (onset between 2 and 6 months); and Infantile Anorexia (onset during the transition from bottle or breast to spoon and self-feeding).

During the first 2 months, successful feeding requires the infant to achieve a state of calm alertness. Infants who have difficulty with state regulation may be difficult to calm. Even though they may feel hungry, they may be unable to reach or maintain the necessary state of calm alertness or they may be too sleepy, too agitated or too easily distracted by stimuli in the environment to complete or even begin a feeding. The infant may fail to gain weight. As the mother becomes more worried, her ability to soothe her infant may deteriorate. A vicious cycle may become established, similar to the one that perpetuates “persistent colic” (see pp 140–141).

Feeding disorder of reciprocity has its onset beyond 2 months of age. An infant older than 2–3 months has the ability to respond to and initiate social interactions with its caregiver. The dyadic relationship includes communicative behaviors such as mutual smiling, cuddling with holding, and mutual vocalizations. Feeding is a major focus of mutually pleasurable engagement during which cognitive and emotional development accompanies physical satisfaction and growth. If, during this stage of development, the caregiver is unresponsive to the infant’s presence or signals, the infant may withdraw, become depressed, and fail to learn behaviors that foster nurturing. Instead of the social smile, he or she may avoid eye contact. Instead of cuddling and molding into a comfortable feeding position, he or she may be either stiff or limp. A caregiver’s failure to emotionally attach to her infant impairs the infant’s ability to become attached to the caregiver. It may become passive, lethargic, and disinterested in food [16]. In the absence of environmental stimulation, such infants tend to engage in self-stimulatory behaviors, such as head-rolling or rumination. Growth and development lag, malnutrition, and decreased resistance to infection may result in death of the infant or, if it survives, a damaged capacity to form attachments in later life.

Infant anorexia is another feeding disorder that may impair growth. Its onset occurs between 6 months and 3 years, a period during which the infant becomes increasingly able to function more independently and willfully. The offer of food by spoon normally becomes an interaction during which any discordant desires of toddler and mother need to be negotiated. This may be especially difficult in toddlers who, by temperament, are easily distracted. Feedings take too long. The parent tries harder to get food into the child’s mouth. Attempts to cajole or trick the child into taking food are met with refusal to open, refusal to swallow, turning away, throwing food or utensils, or climbing out of the high-chair. Parents become increasingly worried as the child who seems to never be hungry, is increasingly difficult to feed, and begins to lose weight. Chatoor found that “…difficult infant temperament was associated with higher mother-infant conflict during feeding…the most difficult infants demonstrated the highest levels of conflict and growth failure.”

FTT can occur in infants who eat more or less adequate amounts of food, but fail to retain what they have taken in. This is exemplified by two functional vomiting disorders of infancy: “Nervous Vomiting” and Infant Rumination Syndrome (IRS).

Before considering these two vomiting syndromes that impair growth, it is important to recognize that about 50 % or more of healthy infants repeatedly vomit or regurgitate during the first 6–18 months of life. This kind of vomiting in normal infants and has been termed “innocent vomiting” [5]. It may range from effortless regurgitation to projectile vomiting. Its main characteristics are that there is no associated pain, nausea, loss of appetite, or underlying organic disease. It does not respond to dietary, positional, or pharmacologic measures. It does not impair weight gain, presumably because, if feedings are given liberally, to satiety, the infant compensates for what has been lost by taking in more. Innocent vomiting resolves spontaneously by or before 12–18 months of age. It is an important consideration in infants who fail to thrive because innocent vomiting plus growth failure may be mistaken for organic disease (e.g., gastroesophageal reflux disease or GERD). This may result in failure to diagnose and treat existing FTT and, instead, impose stressful diagnostic tests in pursuit of nonexistent diseases.

“ Nervous vomiting” was described by the British physician, H.C. Cameron, in 1925 [17]. It is often associated with failure to thrive. It may mimic hypertrophic pyloric stenosis radiologically [5]. Nervous vomiting is a visceral reaction to stress or excitement causing the stomach’s motility to be functionally altered, delaying passage of food into the intestine. Food is retained in the stomach longer than normally, keeping it as a reservoir for vomiting. Infant–mother interaction becomes increasingly distressed as vomiting increases and weight lags. A vicious cycle becomes established as a result of a breakdown in the nurturing relationship which, in turn, causes irritability, vomiting, and feeding difficulties leading to FTT (see Fig. 7.1).

Once suspected, the diagnosis of FTT associated with nervous vomiting can be made by a positive response to a therapeutic trial of comfort [5]. This includes simultaneous efforts to relieve both the infant’s and the parent’s distress. Cameron wrote that, “treatment, if it is to be successful, must aim not so much at controlling the vomiting as at allaying the nervous unrest” [17]. This begins a therapeutic process that heals the parent–infant relationship and is necessary for continued improvement beyond the period of clinical management.