Faltering growth (failure to thrive) in babies and children: causes, assessment and support

Faltering growth is the term NICE uses for a baby or child whose weight is increasing more slowly than would be expected for their age and sex. The older phrase failure to thrive describes the same situation and is still widely used by families and in some health information, but it can sound harsher than it is. In most children the picture is one of a feeding or eating problem that can be understood and improved, rather than a serious hidden disease.

Healthy children do not all grow at the same pace, and a small child is not necessarily a child with a problem. NICE Clinical Knowledge Summaries explain that UK growth charts have centile lines. A centile marks the weight or height below which a given percentage of children of the same age and sex will fall. What matters most is the direction a child is travelling over time: a child who gains steadily along a low centile is in a very different position from one whose measurements drift down across the chart.

The guidance separates two situations. The first is weight loss in the first days after birth, which is common and usually reflects body fluid adjustments. The second is slow weight gain in older infants and children, which is the subject of most of this guide.

NICE guideline NG75 says it is common for newborn babies to lose some weight in the early days, that this usually stops after about 3 or 4 days, and that most babies are back to their birth weight by 3 weeks of age. NICE CKS adds that a loss of up to 10% of birth weight is common and usually relates to fluid shifts.

A loss of more than 10% of birth weight, or a baby who has not returned to birth weight by 3 weeks, may point to feeding that has not been established well. In that situation the guidance asks for a clinical assessment, a detailed feeding history and, where appropriate, someone with suitable training to observe a feed. Feeding support is the first step. NICE also notes that topping up a breastfed baby with formula can help weight gain but often ends breastfeeding, so if formula is used the mother should be supported to keep breastfeeding and to express milk where possible.

Concern usually starts when a health visitor, GP or practice nurse plots a child's weight and sees it has dropped across centile lines. NICE NG75 suggests thresholds for concern based on how far weight has fallen. These depend on the child's birth weight centile: a fall across one or more centile spaces if the birth weight was below the 9th centile, two or more if it was between the 9th and 91st, and three or more if it was above the 91st. Current weight below the 2nd centile for age is also a threshold, whatever the birth weight.

If there is a concern the child is weighed, and length (up to 2 years) or height (over 2 years) is measured and plotted alongside earlier readings. Parents' heights can help, because NICE says a child whose length or height sits well below the range predicted by the parents may have undernutrition or a primary growth disorder. For children over 2 years, body mass index may be calculated and plotted. Readings are recorded in the parent-held Personal Child Health Record, often called the red book.

• Weight on its own can be misleading after one reading; the trend over several measurements is what counts.

• Weighing too often can add to parental anxiety, because small short-term changes are normal.

• Weight loss after the early days is unusual and may justify closer follow-up.

NICE CKS says faltering growth in older infants and children is caused by inadequate calorie intake (the most common cause), inadequate absorption of nutrients, or increased calorie demand. Often several factors overlap and a single cause cannot be identified. NICE NG75 is explicit that it may not be possible to find a clear cause, and that difficulties in the interaction between parent and child may contribute without being the main problem.

The risk factors listed by NICE CKS fall into a few groups. Parents and carers can find it reassuring that many are practical and addressable.

• Feeding problems: ineffective suckling, too little breast milk, or incorrect preparation of infant formula.

• Medical conditions: for example constipation, cleft palate, gastro-oesophageal reflux, coeliac disease or diabetes.

• Preterm birth, neurodevelopmental concerns and maternal postnatal depression or anxiety, which NG75 lists as associated factors.

• Mealtime patterns: food aversion or avoidance, lack of appetite, or difficulty responding to a child's mealtime cues.

• Poor access to healthy food and wider family stress such as housing, financial or relationship problems.

• Child maltreatment, which is listed among the risk factors and is one reason professionals assess the whole family context.

NICE NG75 recommends a clinical, developmental and social assessment together with a detailed feeding or eating history. Where it would help, someone with appropriate training may watch a feed or mealtime. Parents may be asked to keep a food diary recording what and how much the child eats and how mealtimes go.

Investigations are deliberately limited. NICE suggests considering a urinary tract infection and, if the child eats gluten-containing foods, coeliac disease, and carrying out further tests only if the clinical assessment points to them. The guideline says that other investigations are unlikely to reveal an underlying disorder in a child who looks well. If new symptoms or signs appear later, the need for tests is reconsidered.

Management begins with a plan agreed with parents or carers that sets specific goals, says when the child will be reviewed and describes what monitoring will happen. For most children the focus is on feeding and mealtimes rather than on medicines.

NICE NG75 lists practical points that may be discussed. These include relaxed and enjoyable mealtimes, eating together as a family, letting young children feed themselves and be messy, setting reasonable boundaries without punitive or coercive approaches, and a regular routine such as three meals and two snacks a day. NICE also advises that very large amounts of energy-dense drinks, including milk, can reduce a child's appetite for other foods.

NICE NG75 suggests weighing usually no more often than daily if under 1 month old, weekly between 1 and 6 months, fortnightly between 6 and 12 months and monthly from 1 year. Length or height is measured at intervals of no less than 3 months. This pacing is meant to give a meaningful picture without turning every week into a source of worry.

Discussion with, or referral to, a paediatric specialist service is advised if there are symptoms or signs that may point to an underlying disorder, if the child does not respond to measures delivered in primary care, if growth in length or height is slow or there is unexplained short stature, if there is rapid weight loss or severe undernutrition, or if there are safeguarding concerns. A paediatrician, paediatric dietitian, speech and language therapist with feeding expertise, clinical psychologist or occupational therapist may become involved depending on the child's needs.

If you are worried that your baby or child is not gaining weight, is not feeding well, or has dropped across the lines on their growth chart, speak to your health visitor or GP. Do not wait for the next routine check. Seek urgent advice from NHS 111, or call 999 or go to A&E in an emergency, if a baby or child is drowsy, floppy, hard to wake, breathing with difficulty, showing signs of dehydration or seems seriously unwell.

The NHS route is the one described in the NICE guidance: assessment and support through the health visitor and GP, with paediatric services for children who need them. Some families also choose to see a private paediatrician or dietitian, particularly if they want a second opinion or faster access. In general terms, any clinician should follow the same assessment steps, and the child's growth measurements from the red book are a useful starting point to share.