Failure to thrive (FTT), otherwise called growth faltering, slow growth or poor growth, is a condition that refers to when a baby does not gain weight and does not grow as they need to. Although every baby is unique, there are some expectations around the amount of weight they need to gain to grow normally. Development, brain growth and general health can all be affected when a baby’s weight and size do not increase over time.

What is failure to thrive?

Babies who are diagnosed as being 'failing to thrive' weigh persistently below the 3rd percentile and have crossed 2 or more percentiles over time. All babies have periods when they gain or lose weight. Most babies lose weight after they are born — on average, between 5-10% in their first week. However, the majority then regain their birth weight by 2 weeks of age.

Sometimes a baby’s weight is stable, but generally, it is unusual for babies to lose weight unless they are unwell.

When a baby is consistently losing weight and not growing at the expected rate for their age and gender, they may be diagnosed as having 'failure to thrive'.

What causes failure to thrive?

Physical or organic causes

There are a few reasons why FTT can happen. Sometimes there’s a physical or organic reason which causes the baby not to absorb or metabolise nutrients. This means they are unable to use the food (milk or solids) they’re eating to fuel their growth.

Common medical conditions causing FTT include:

• allergies to food and milk
• prematurity
• gastro oesophageal reflux disease (GORD)
• conditions which cause vomiting
• conditions which demand more energy — cardiac (heart) problems, respiratory issues, infection or hormone disorders

Environmental causes

Environmental factors can cause FTT, most commonly because the baby isn’t being fed the right amount of food to fuel their growth.

Some common environmental causes for FTT include:

• lack of opportunity — the baby is not offered regular, nutritious milk and/or food
• family homelessness and/or poverty
• parents experiencing mental health issues and an inability to provide adequate food
• parents missing their baby’s cues for hunger

Combination of causes

Sometimes FTT is caused by a combination of medical and environmental factors. Babies can refuse to feed or become fussy feeders because of an undiagnosed and untreated medical condition. Babies can also continue to be fussy feeders after they have recovered from an illness.

Babies who were small for gestational age (SGA) or premature, can take longer to gain weight after birth and ‘catch-up’ with babies of the same age.

What if there’s no apparent cause for failure to thrive?

It’s not always clear what causes a baby to fail to thrive and sometimes no specific cause is found. This makes it difficult for parents who may feel they’re doing all they can to feed their baby regularly and support them to grow.

It’s not uncommon for parents to feel stressed and anxious about their baby’s growth, especially when their baby is diagnosed with FTT. Just as a parent’s emotional distress can contribute to FTT, parental anxiety is a common outcome when a baby does not grow as they need to.

However, some babies are smaller because of genetics. Parents who are shorter and smaller than average are more likely to have children with the same characteristics.

How do I measure my baby’s growth?

It’s relatively easy to measure how your baby is growing. Their weight, head circumference and length are all indicators of how healthy they are and how big they are getting. Growth charts are used to plot changes in a child’s measurements. Since 2013, WHO growth charts are recommended in Australia to measure children aged between birth and 2 years.

On average, most babies will:

• double their birth weight by around 4 months of age, and triple it by 13 months
• increase their birth length 1.5 times in the first 12 months
• increase their birth head circumference by around 11 cm in 12 months

What happens if my baby has failure to thrive?

Your baby will need to be examined by a paediatrician. Sometimes more frequent breast or formula feeds and for babies over 6 months, increased solids, are enough to provide extra kilojoules to support increased growth. If FTT is not related to feeding or an underlying disease, medical practitioners can investigate further.

Regular weight and growth checks are important for babies who are diagnosed as having FTT. Check with your child health nurse, doctor and paediatrician to monitor your baby’s growth.