An Update on the Diagnosis and Management of Faltering Growth and Catch-Up Growth in Young Children

The term “failure to thrive” was first introduced in the 20th century to describe growth in orphaned children, but as this term was associated with maternal deprivation and a failure of parenting, it was changed to “faltering growth” (FG) to remove the negative stigma [1]. FG is described as a slower rate of weight gain in childhood than expected for age and gender [2].

Many terms have been used interchangeably for FG, including malnutrition, stunting, wasting, and underweight, but when assessing the definitions as set out by the World Health Organisation (WHO) and exploring the different definitions for FG, there are distinct differences. Although protein-energy (PE) malnutrition was historically seen as a nutritional deprivation, particularly among children in low- and medium-income countries, and FG in more affluent societies, it is now acknowledged that both occur in all countries [3]. The main difference between undernutrition using the WHO criteria and the more recent definitions for FG is that the latter is a dynamic process of growth reduction over time using weight-for-age, whereas undernutrition, using the WHO definition, is a static measurement at a point of time for weight-for-height (wasting), height-for-age (stunting), and weight-for-age (underweight) (Box 1) [2, 4, 5].

While growth centiles provide critical information on the dynamic process of growth over time, not all countries use the WHO growth centile charts for all paediatric ages (i.e., Centres for Disease Control and Prevention [CDC] recommend WHO growth chart only between 0 and 2 years) or they are based on the WHO database but use different centile lines (i.e., Royal College of Paediatrics and Child Health [RCPCH] growth charts). Therefore, a drop in centiles using different growth charts would not yield the same result, making a definition of FG, such as the one from the National Institute for Health Care Excellence (NICE) in the UK, of a drop of 2 centile lines, not useful, unless the RCPCH growth centiles are used.

As a universal alternative, a drop in weight-for-age z-scores, using the WHO Anthro Software (https://www.who.int/tools/child-growth-standards/software), has been considered. Z-scores can be uniformly used to interpret growth (irrespective of local growth charts) and are also used in research, allowing for the comparison of data between different healthcare settings. Victora et al. [3] assessed worldwide timing of growth faltering using national anthropometric surveys from 54 countries. This study found that weight-for-age starts close to the standard and falters moderately until reaching approximately −1 z-score weight-for-age at 24 months. The authors of this study highlighted the importance of a window of opportunity of intervention within the first 2 years of life, based on these data and revisited these data in 2021 with the same message [8] (see Box 2 for a practical example).

Since then, some publications have used a downward trajectory of = /> 1 z-score in weight-for-age as a definition for FG [9, 10]. A recent expert opinion publication by Cooke et al. [6] also suggested that a drop of weight-for-age of 1 z-score over 1 month or more, which does not include the first 2 weeks of life, warrants an evaluation for FG. The authors of this paper further recommend that the time frame for the falling of weight should be sufficient to ensure that acute weight loss, such as that occurring rapidly with an episode of vomiting and diarrhoea, is not classified as FG. This definition allows for the universal use of WHO z-scores and would permit the better determination of prevalence among different populations [3].

The prevalence of FG among infants varies depending on the definition used, the population (i.e., healthy vs. sick children), and whether the data were generated in high-, middle-, or low-income countries [11]. Olson et al. [4] reported that 27% of their population of children in a primary care setting in Denmark (comprising families of low, medium, and high income) met one of the criteria for FG [4]. However this seems much higher than the reported prevalence of 5–10% range in the primary care in the USA, which is related to the definition used [12]. While the prevalence of malnutrition, as per World Health Organisation (WHO), is well described in low- and middle-income countries, this is not the case for FG. Studies from Nigeria (primary care), Thailand (primary care), and Iran (children admitted to hospital) have found the prevalence of FG in children to be 19.8%, 17.8%, and 36.6%, respectively, but they all used different criteria [13‒15]. The prevalence of FG increases significantly when this is assessed in a hospital setting including children with both chronic and acute illnesses, where the prevalence is still thought to range between 14% and 24% in high-income countries [16, 17], and in middle-income countries such as South Africa and Turkey, it is between 34 and 40% [18]. Puls et al. [19] found that from 10,499 children (40.8% with chronic conditions) that were hospitalised due to FG in the USA, 14.1% were readmitted for FG within 3 years and 4.8% within 30 days. In low-income settings, Mertens et al. [20] has shown from a pooled analysis of 33 longitudinal studies that children with multiple growth deficits exhibited higher mortality rates from birth to 2 years of age than children without growth deficits (hazard ratios 1.9 to 8.7).

The treatment of FG has a significant fiscal burden for any healthcare system, with a recent systematic review by Mdege et al. [21] assessing the cost and cost-effectiveness of treatment of wasting, oedema, and FG. Overall, this systematic review found that initiation of treatment in outpatient settings is highly cost-effective when compared to doing nothing or no programme implementation scenarios, using country-specific World Health Organisation (WHO) GDP per capita thresholds. In this systematic review, only one study from 1987 assessed the impact of FG and found that in their treatment program, 100-g weight gain costs USD 308 [22]. In the UK, a model of the cost of FG indicated a cost of GBP 2,783 in 2013, driven in particular by complications and comorbidities [2].

Apart from the health-economic burden, the early recognition of FG is even more important for the child when considering the short- and long-term consequences, which include reduced school performance and cognitive development, and has been associated with increased risk of morbidity, mortality, and prolonged length of hospital stay [20, 23, 24]. Long-term FG is associated with reduced educational and economic performance in adulthood [25]. This publication is aimed at reviewing the current evidence around diagnosis and management of FG in children in low-, medium-, and high-income countries.

The causes of FG are traditionally classified into being either illness-related (medical causes, including congenital cardiac defect, neurological and gastrointestinal disorders) or non-illness-related (socioeconomic, food insecurity, low-quality diet, behavioural, environmental factors) [26]. However, such a rigid classification does not acknowledge the interplay between illness- and non-illness-related FG and the fact that poor growth may be multifactorial [6]. This has been well demonstrated by a study by Ramsay et al. [27], who found that a significant number of the children who were classified with non-illness-related growth faltering had subtle neurodevelopmental disorders and pathophysiology (i.e., delayed sucking ability), but were otherwise medically well. Additionally, feeding practice commonly changes due to an underlying diagnosis, concern about the growth of a child, or a traumatic experience [28]. Overall, the cause of FG can be attributed to 3 primary factors [29]:

• Increased requirements – this may be due to illness (i.e., congenital heart disease).

• Increased losses – this may be due to vomiting, diarrhoea, or sodium losses in urine.

• Reduced intake – this may be due to feeding difficulties which could be related to illness (i.e., reflux) or feeding practice at home.

Figure 1 demonstrates the interplay between illness- and non-illness-related factors that can lead to FG.

Critical to the diagnoses and the management of FG is a detailed history, which includes the following [2, 10]:

• a)

  Medical history: pre- and perinatal history, previous illnesses, current and past medication, and vaccination status.

• b)

  Family history: genetic conditions, parent health status including conditions that may impact the care a child is receiving. This should also include information on stress at home and history of mental health.

• c)

  Living environment: housing conditions, availability of clean water, and sanitation.

• d)

  Socioeconomic status: employment status of parents and type of employment including access to resources.

• e)

  Caregiver information: who primarily cares for the child and childcare arrangements.

• f)

  Developmental milestones: is the child achieving age-appropriate milestones or is there any developmental delay.

• g)

  Parent-child interaction: this requires observation and may need a feeding/play assessment.

• h)

  Current symptoms: gastrointestinal, respiratory, and other (i.e., fatigue, irritability, or other signs of systemic illness).

A physical examine also forms an essential part of the assessment of a child with FG and provides a subjective view of lean and muscle mass and may also highlight further symptoms of concern that may contribute towards understanding the underlying reasons for the FG. The impact of emotional deprivation (i.e., neglect) and safeguarding concerns also need to be considered with a clinical assessment [2, 30]. Critical questions around body composition should include the following:

• Is there evidence of temporal or facial wasting?

• Are there bracelets of fat around the wrist?

• Are there rolls of fat on the thighs?

• Looking from the side – are there buttocks, or are they flat and sagging?

• Are there protruding ribs or hips?

• Does the stomach look out of proportion (e.g., distension)?

To identify a child with FG, it is important to review their growth trend by measuring the child’s weight/stature accurately using the method and the equipment described by the WHO (https://iris.who.int/bitstream/handle/10665/43601/9789241595070_B_eng.pdf?sequence=2&isAllowed=y). While most definitions for FG are primarily based on weight-for-age, it is critical that the child’s stature (length for <2 years of age and height >2 years of age) and head circumference (if < 2 years of age) is also assessed to establish long-term growth. Children can be classified as having both FG and suffer from undernutrition (defined by <−2 z-score for weight-for-height or height-for-age).

Figure 2 provides an example of growth curves using weight-for-age for normal growth, FG, and underweight as per WHO definitions. The evaluation of nutritional biomarkers that may indicate a vitamin and/or mineral deficiency is complementary to the anthropometrical assessment. The WHO classifies vitamin and mineral deficiencies as “hidden hunger,” and in particular, zinc, iron, iodine, and vitamin A have been identified as a significant concern in children worldwide [7]. Vitamins and minerals are not only co-factors for growth but may be a major contributing factor to FG. Golden divided nutrients into type I and type II nutrients: type I (most vitamins and minerals) are those that are needed for particular biochemical functions in the body and if these nutrients are severely deficient, the child will develop specific symptoms and signs of deficiency, while type II nutrients are the growth nutrients (amino acids, fat/carbohydrates, sodium, chloride, zinc), with deficient intake of any one of these nutrients, the child will not grow [31].

A detailed dietary history provides critical information relating to dietary intake and feeding patterns [32]. Important questions to consider when assessing the dietary intake include the following:

• Is a child being breastfed (and assess the efficacy of breastfeeding if the answer is affirmative)?

• What type of milk is usually given to the child if not breastfed (include volume and frequency)?

• What is the quantity of the main meal eaten? Is it appropriate?

• What is the mealtime environment?

• Does the child have a feeding difficulty which may include gagging/choking on textured foods, food refusal, distress during a meal?

• Are foods eliminated (for religious or due to food hypersensitivity reasons)?

While food insecurity has been a recognised contributing factor to FG, the level has increased in particular after the COVID pandemic worldwide [33]. There is a validated 2-question screening tool for healthcare professionals to identify families with food insecurity, which should form part of routine clinical practice [34]:

AND

The nutritional assessment supports the consideration of energy and protein requirements, which should ideally be tailored to the underlying illness (i.e., critical illness, neurodevelopmental delay, congenital cardiac defect) and non-illness-related causes and where appropriate, published guidelines should be used [6]. These vary greatly between the age of the populations, the pathophysiology of disease, losses through vomiting, diarrhoea, and urine, and medical management [6]. Where no guidelines are available, the WHO/FAO/UNO guidelines for energy and protein requirements should be used (which are appropriate for infants <1 year of age) and are illustrated in Table 1 [35]. Protein requirements are based on actual body weight. The focus should be on weight gain and attaining growth with optimal balance between lean and fat mass (73% lean and 27% fat mass) in the accrued tissue [35]. An ideal PE ratio for catch-up growth has been shown to be 8.9–12% [31]. Enriching products with modular additions of fat and carbohydrate alone often results in PE of 4.5–6%, which does not favour optimal catch-up growth in growth faltering infants [36]. The above increase in percentage of PE should only be applied in children with FG and normalised when catch-up has occurred. Studies have shown that higher intakes of total and protein (in particular animal protein like cow’s milk protein) during infancy were associated with higher body mass index in childhood and adolescence [37].

It is important to ensure that any identified vitamin and/or mineral deficiencies are corrected for and that children receive sufficient vitamins and minerals to aid catch-up growth [6]. Multiple micronutrient supplementation, including vitamins A and D, zinc, and iron (Table 2), are effective in promoting catch-up growth in children under 5 years and should be considered a routine supplement in children with FG [11, 31] (see Box 2 for a practical example).

There are not many studies that describe management options for children that are breastfed and have FG. Rana et al. [38] assessed feeding interventions for FG for the first 6 months of life and identified 47 studies. The following interventions had a positive effect on anthropometric outcome: macronutrient-fortified formula, cream supplementation, and fortified human milk formula [38]. Interventions comparing human breastmilk/donor milk with formula had mixed effects. Overall, only human milk compared to formula intervention had a positive effect on morbidity, while none of the interventions had any positive effect on mortality [38]. However, all of the aforementioned outcomes were found in preterm infants and/or infants that were small for gestational age. It is known that growth patterns and nutritional requirements differ between term and preterm infants and that catch-up growth requirements are distinctive for infants that were born small for gestational age. All current guidance on the management of FG support breastfeeding and promotion of optimal breastfeeding practice to be the foundation of every early intervention strategy and therefore assessing technique and supply of breastmilk is a first priority [6].

The WHO has recently published the new guidelines on the prevention and management of wasting and nutritional oedema (acute malnutrition) in infants and children under 5 years of age [39]. For the first time, they have also included guidance on infants less than 6 months of age that are breastfed. It is however important to note, that these guidelines are specifically written for wasting and nutritional oedema and may therefore not be applicable for all children with FG, unless they also meet the WHO criteria for wasting and nutritional oedema. The WHO guidelines provide more specific guidance for infants below 6 months of age, quoted below [39]:

• a)

  “For infants less than 6 months of age at risk of poor growth and development, health workers should conduct comprehensive assessments of the mother/caregiver-infant pair and follow best practices for management of breastfeeding/lactation challenges and underlying factors contributing to these challenges.”

• b)

  “Decisions about whether an infant less than 6 months of age at risk of poor growth and development needs a supplementary milk in addition to breastfeeding must be based on a comprehensive assessment of medical and nutritional/feeding needs of the infant, as well as the physical and mental health of the mother/caregiver.”

• c)

  Infants who are less than 6 months of age with severe wasting and/or nutritional oedema who are admitted for inpatient care:

  • -

    Should be breastfed where possible.

  • -

    Should also be provided a supplementary feed (Commercial [generic] infant formula or F-75 or diluted F-100 may be given, either alone or as the supplementary feed together with breast milk).

If children are not treated in an outpatient setting, the WHO complementary feeding guidelines suggest the careful consideration of infant formula. It is only recommended when specific home conditions are met, including safe water and sanitation in the household, sufficient infant milk formula is available to support the normal growth and development, and the mother or caregiver can prepare it cleanly and frequently enough so that it carries a low risk of diarrhoea and malnutrition, among other adverse outcomes [40].

In formula-fed infants with FG or where an infant formula is indicates as per WHO guidelines above, it is important to assess volume consumption and other causes of FG related to the formula or food consumed, where applicable (i.e., cow’s milk allergy, food protein-induced enteropathy) [41]. Where possible a ready-to-use energy-dense feeds with proven efficacy should be used, as these have a PE ratio conducive for catch-up growth [6, 42, 43]. In many countries, these may not be available and therefore suitable locally available powdered feeds (i.e., F-75 and F-100) can be used, applying WHO hygiene safety for mixing [44] (see Box 2 for a practical example).

Consensus guidance, based on evidence, suggests that the modular additions of only fat and/or carbohydrates to infant formula should be avoided, as this reduces the protein:energy ratio [6, 45]. When only carbohydrates and/or fat are added to infant feeds the energy percentage from protein is significantly reduced, which has been shown to impact on the ratio of lean to fat mass in catch-up growth. The addition of carbohydrates increases the osmolality of feeds, which may affect gastric emptying kinetics with a potentially negative impact in infants that are already medically fragile [6, 42]. In cases where the requirements of the nutritional management plan cannot be met through oral intake, the plan should include recommendations for enteral (i.e., nasogastric of gastrostomy) feeding, including monitoring by a multidisciplinary nutrition support team to minimise the risk of enteral nutrition associated complications [46].

In infants with FG, where complementary foods have been commenced, the fortification of accepted foods and advice on foods that are naturally energy-dense, locally available and culturally acceptable, form an essential part of the management [6]. This may include the addition of nut butters, dairy products (when affordable), soya products, or other plant-based proteins to food. Commercial ready-to-use therapeutic food (RUTF) are already being used and recommended where paediatric undernutrition is prevalent [40]. The United Nations International Children’s Emergency Fund procures and distributes an estimated 75–80 percent of the world’s RUTF supply [47]. Efficacy has been proven of these specialist RUTF complementary foods and shown significant catch-up weight gain [48].

Feeding difficulties are a common problem in children with FG, either as a cause of the underlying illness, which can lead to fear of eating/low appetite or due to the disruption of normal feeding related to feeding style (i.e., non-responsive feeding) as illustrated in Figure 1 [49]. Healthcare professional do need to address any underlying feeding difficulties as part of the nutritional management, as these do not only impact of macro and micronutrient intake but also cause great distress [50] (see Box 2 for a practical example).

The term catch-up growth was defined by Prader in 1963 as the “acceleration in growth in response to recovery from illness or starvation” [51]. Physiologically, it has been defined as an increase in weight-for-age after a period of “growth faltering,” ideally to the original weight-for-age z-score [6].

The monitoring of a child with FG is a critical part of the management. It is therefore important that a target for catch-up is set, guided by the nutritional assessment and that this target steers the frequency of follow-up and growth measurements. Such a target is not only helpful to guide healthcare professionals in the management of an individual child with FG, but helps prevent excessive weight gain, which is a concern and risk factor for the development of obesity and cardiovascular disease in later life [52, 53].

Growth acceleration is defined as upward centile crossing for weight-for-age and, in contrast to catch-up growth, is not in response to FG. It occurs spontaneously (e.g., in infants who are small for gestational age) and can be promoted, e.g., by overfeeding or formula-feeding compared to breastfeeding [6]. Both catch-up growth and growth acceleration involve upward centile crossing in weight, but only catch-up growth follows recovery from illness or a period of undernutrition and is the desirable goal to achieve for FG. Figure 3, illustrates the weight gain trajectory of growth acceleration.

The consensus publication by Cooke et al. [6] suggested that a pragmatic target for catch-up growth would be for the child to return to the original centile or z-score before experiencing growth faltering, given the child was in good nutritional status before the insult occurred. Acknowledging the importance of body composition, it was also suggested that attention should be paid to changes in length-for-age as a simple-to-measure approximate proxy of lean mass [54].

While no clear guidance has been published for the frequency of growth monitoring, Golden has published direction on catch-up rate (in days) based on the level of weight loss and specific length (Table 3). This provides healthcare professionals with an estimation on follow-up based expected rate of catch-up but needs to be individualised based on the age, the underlying cause and whether the child has FG only or is also undernourished as per WHO criteria. For children with wasting and oedema, the WHO has recently published clear guidance for both discharge from inpatient care and exit from nutritional treatment [39].

FG refers to a slower rate of weight gain in childhood than expected for age and gender. The term FG has replaced “failure to thrive” as this is more descriptive and less pejorative. FG occurs in low-, middle-, and high-income countries, and the active monitoring of growth over time should form part of standard practice for healthcare professionals. There is concern related to the varying definitions to recognise FG, which makes the assessment of prevalence between diagnoses, healthcare systems, and countries challenging. It has been proposed to consider FG when there has been a drop of 1 z-score in weight-for-age over time using the WHO growth standards. Promoting catch-up growth with individualised dietary advice that supports breastfeeding when available and the appropriate energy-dense formula and complementary food is critical. Monitoring children at intervals that match the expected velocity of catch-up is important to avoid excessive weight gain beyond what the normal healthy weight is for the individual child. The assessment of FG should also include the consideration of food insecurity and feeding difficulties.

Dr. Meyer reports grants with Danone/Nutricia, honoraria from Reckitt Benckiser, Nestle Nutrition Institute, Danone, Abbott Nutrition, and consultancy fees from Else Nutrition and CoMISS supported by Nestle Nutrition.

No funding was received for the writing of this publication.

Dr. Meyer was the sole contributor to this article.