Variations In Normal Growth

If your baby is not gaining weight as expected, one of the first things to consider is if this could be due to a variation of normal growth. Not all health professionals are aware of variations in normal growth and as a result they are often mistaken as poor growth. Being aware of variations in infant growth could spare you unnecessary anxiety.

What does a variation in normal growth mean?

While all babies become larger over time, they don’t all follow a typical growth pattern. Typical growth represents one path that leads a baby to achieve his growth potential. However, there are many paths that can lead to the same destination.

Variations in normal growth represent alternative pathways that enable individual babies to achieve their growth potential.

The various normal growth patterns that cause the most confusion, and needless concern, include:

Natural decline in growth rate.
Growth spurts and plateaus.
Formula-fed babies’ growth.
Catch-up and catch-down growth.
Constitutional growth delay.
Genetically lean baby.

Note: A natural decline in growth rate and growth spurts and plateaus are in fact typical growth displayed by all healthy babies. However, they’re included in this article because people who are unaware of variations in normal infant growth may be unaware of these as well.

1. Natural decline in growth rate

Babies don’t continue to gain weight at the same rate over the long term. As they age, their rate of growth, and thus the amount gained on a weekly or monthly basis, gradually declines. This becomes apparent when looking at an infant growth chart.

All 3 major indicators of growth, i.e. weight, length and head circumference, are represented by curves on an infant growth chart. A curve indicates deceleration or decreased velocity over time, or in regards to infant growth a curve represents a gradual decline in babies’ rate of growth as they mature. If babies were expected to continue to gain weight at the same rate over the long term this would be reflected as a straight diagonal line on an infant growth chart.

Our article on average weight gain for age provides further examples of how babies’ weight gains decline as they mature.

Misdiagnosis

The natural decline in babies’ rate of growth can be mistaken as poor growth.

While it’s obvious that babies grow at a slower rate as they mature once it’s pointed out, not all parents or health professionals consider this until it is. Health professionals sometimes unknowingly mislead parents by quoting average weight gain figures for younger babies. Or parents might incorrectly assume that figures quoted for their baby at a younger age remain relevant even though baby is now older. Either way, expectations about how much weight a baby should gain could be unrealistic and unachievable.

A baby will show signs of being well fed when growth naturally declines. If growth is poor due to underfeeding these signs won’t be apparent.

2. Growth spurts and plateaus

Babies’ growth does not occur in a linear pattern where every day baby gets a little heavier and longer. Daily measurements of babies’ growth show that growth is episodic, and not continuous. Dramatic spurts of rapid growth occur in a single day, separated by periods of no measurable growth (growth plateaus) that can last for days or weeks.

Growth spurts

Leading up to a growth spurt a baby’s appetite increases. He demands extra breastfeeds both day and night. Or drains his bottles and wants more. Or eats solids like he’s never going to stop. He gains weight over a short period of time. Growth in length, which can involve an increase 0.25 to 0.6 inch (0.5 cm to 1.65 cm), occurs within a single day. [Source].

Some claim to be able to predict the age babies undergo growth spurts. However, with the many variables that influence a baby's growth this is not possible. Each baby is an individual and as such will grow at his or her own pace.

Growth plateaus

During growth plateaus a baby’s weight and length remains relatively unchanged for days or weeks. In comparison to his appetite and feeding behavior prior to a growth spurt, he’s now less demanding, goes for longer stretches between feeds, breastfeeds for shorter periods, leaves milk in his bottles, and is not as interested in eating solids.

Whether plateaus in growth are noticeable largely depends on how often baby is weighed. The more frequently he is weighed, the more likely it is that these periods of no measurable growth will be detected.

Daily weight checks will show plateaus in growth.
Weekly weight checks might show stagnant growth from one week to the next.
Monthly weight checks are unlikely to show stagnant growth due to a growth plateau because it's likely that baby will have had a growth spurt during that time.

The younger the baby the faster he grows and the more frequent growth spurts occur. While plateaus in growth are not always obvious when monitoring the growth of babies, they are more apparent in baby's second year of life and beyond because growth plateaus extend for much longer periods of time as children mature.

Misdiagnosis

Most people are aware that babies and children have growth spurts, but not all are aware that periods of no measurable growth are also a normal part of the growth process. And they may not be aware of how growth plateaus affect a baby’s appetite.

If it becomes apparent that a baby’s growth has plateaued from one weight check to the next, this can be mistaken as poor growth. And this may be erroneously blamed on reduced milk intake when in reality reduced milk intake is because baby's growth has plateaued.

If a baby is weighed monthly, and therefore plateaus in baby’s growth not observed, then what concerns parents most is baby’s decreased appetite. This will be more obvious when a baby is bottle-fed than if he was breast-fed solely because it’s possible to tell how much a baby drinks from a bottle. During a growth plateau parents might worry that baby is not eating enough for healthy growth.

The difference between reduced appetite due to growth plateau and underfeeding is that a baby shows signs of being fed during a growth plateau.

3. Formula-fed babies' growth

Breastfeeding is the biological normal feeding method for babies; therefore the growth of breast-fed babies reflects the normal growth pattern of babies. The World Health Organization (WHO) recommends that the growth of breast-fed babies is the standard against which all babies are compared. In 2006 WHO released a series of infant growth charts based the growth pattern of breast-fed babies. These are widely used by health professionals today.

What’s normal growth for breast-fed babies is not typical for formula-fed babies. In general, formula-fed babies tend to gain less weight in the first 2 to 3 months compared to breast-fed babies, and more weight from 6 months to 12 months. [Source] (See Average growth for age for comparison between breast- and formula-fed babies’ growth.) The reason for the difference is believed to be due to the types of protein in infant formula

Some might claim that the growth pattern of a formula-fed baby is not normal if it doesn’t resemble the growth of breast-fed babies. However, until such time as manufacturers can produce infant formula that contains proteins that more closely resembles those in human milk, then the typical pattern of growth displayed by formula-fed babies is normal for formula-fed babies.

Misdiagnosis

When the growth a formula-fed baby doesn’t match that of breast-fed babies using WHO infant growth charts, this could be mistaken as poor growth.

Alternatively, if a breast-fed baby’s growth doesn’t match that of formula-fed babies - as largely represented by CDC infant growth charts - this too could be mistaken as poor growth.

4. Catch-up and catch-down growth

After birth one of the strongest influences on a baby’s growth is his genetic endowment, i.e. the physical characteristics inherited from his parents. A baby’s growth can deviate away from and return to his genetically determined path, while in the womb or after birth, for many different reasons.

Catch-up growth

Catch-up growth involves a period of rapid growth – more than an expected range for babies of the same age - that enables a baby’s growth to return to his genetically determined path. Catch-up growth follows a period of growth restriction or delay that caused baby’s growth to deviate away from his natural course. Growth restriction or delay can occur…

In the womb - baby may classified as IUGR at birth.
Due to problems that cause underfeeding.
As a result of illness.
Because of a digestive disorder or medical condition.

Once barriers that restricted baby’s growth are removed - for example, baby is born, he recovers from illness, the digestive disorder or medical condition is effectively treated, or the problem causing underfeeding is corrected - baby will then go through a period of catch-up growth.

During the period of catch-up growth baby will have a healthy appetite. He demands frequent feeds and eats more than expected. Most people are aware of catch-up growth and they’re delighted to see baby eating a lot and gaining large amounts of weight. However, the period of catch-up growth only continues until baby’s growth has returned to his natural path, at which time his rate of growth will gradually slow and appetite drop to within a normal range. (See Catch-up growth for more.)

Catch-down growth

Catch-down growth is the opposite of catch-up growth. Catch-down growth involves a period of slow growth – below an expected range for babies of the same age - that enables a baby’s growth to realign to his genetically determined path. Catch-down follows a period of rapid or extreme growth that caused baby’s growth to deviate away from his natural course. Rapid or extreme growth can occur…

In the womb due to maternal diet, gestational diabetes, or medications given to the mother.
In the early months due to overfeeding.
Due to steroid medications given to babies to treat certain medical conditions.

Once baby is born and thus his growth is no longer under the influence of factors in the womb, or when problems causing overfeeding are corrected, or when steroid mediations are ceased, baby may then go through a period of catch-down growth

During the period of catch-down growth baby may appear to have a poor appetite. But it’s not poor. He displays signs of being well fed. He doesn’t need to eat as much as other babies because he’s growing at a slower rate compared to most other babies his age.

Catch-down growth only continues until a baby's growth has realigned to his genetically determined path. As he gets closer, his growth rate and appetite may become more closely aligned to that expected for age.

Catch-down growth is as healthy and as normal as catch-up growth. (See Catch-down growth for more.)

Misdiagnosis

While most parents and health professionals are aware of catch-up growth, few appear to be aware of catch-down growth, or the circumstances in which it can occur, or the impact it has on a baby’s appetite. As a result catch-down growth is often mistaken as poor growth. And because baby is not eating as much as expected, it’s wrongly assumed that the cause of baby’s slow growth is because he’s not eating enough or his mother has low milk supply.

5. Constitutional growth delay

Constitutional growth delay (CGD) involves a temporary delay in skeletal growth. Baby is usually normal size at birth. Starting from around 3 to 6 months of age his rate of growth is much slower than considered typical for a baby of his age and size. Weight gains are consistently below average.

Tracking his growth on an infant growth chart shows a downward trend as his weight and length cross through multiple growth curves until 2 to 3 years of age. At that time, his growth resumes at a normal rate but his length remains below or parallel to the 3^rd percentile until he reaches puberty. His weight will be at a similar, but not necessarily the same, percentile curve.

As a child, he remains small in comparison to other children of his age and smaller than expected considering the heights of his parents until after puberty when his size returns to normal adult height relative to his parents’ heights.

Usually, a parent or other close family member displayed a similar pattern of growth as a baby and child. They may have been called a ‘late bloomer’ who was smaller than most other children of the same age but ultimately grew to adult height consistent with parents’ heights. CGD can be distinguished from poor growth by X-raying a child’s wrist. An X-ray will show delayed ‘bone age’, which means that his skeletal maturation is younger than his age in years.

A CGD baby’s appetite is small because growth occurs at a slower rate compared to most other babies his age. While baby’s appetite appears small he shows signs of a well-fed baby.

Misdiagnosis

When parents and health professionals overlook CGD, baby’s lower than expected weight gain and the progressive pattern of weight and length dropping to lower percentile curves is usually mistaken initially as poor growth and he may be misdiagnosed as ‘failure to thrive'.

6. Genetically lean baby

Some babies are genetically programmed to be lean. They inherit ‘skinny’ genes. One or both parents or a close family member were lean as a child and may have been classified as underweight or 'failure to thrive' as a baby.

Genetically lean babies are skinny babies. They carry less fat on their bodies compared to most other babies, but they are just as healthy as their chubbier peers.

A genetically lean baby may or may not drink the amount of milk estimated according to his weight and age. He will eat what his body needs and no more. Because he’s lean, parents and caregivers usually try to make him to eat more than he’s willing to eat. Despite being skinny, he has boundless energy and shows signs of being a well-fed baby. (See Skinny baby for more.)

Misdiagnosis

Genetically lean babies are highly likely to be classified as underweight or ‘failure to thrive’. Unfortunately, these days many genetically lean babies can end up being tube fed when all attempts to fatten them fail.

Note: You can not fatten a genetically lean baby, not even with tube feeding. Being genetically lean is not a condition that requires treatment. It simply requires recognition and acceptance that baby is naturally inclined to carry less body fat compared to others.

Consequence of misdiagnosis

Mistaking normal growth variations as poor growth or ‘failure to thrive’ causes needless anxiety for parents. But, that’s nothing compared to other problems such mistakes can cause. Mistaking variations in normal growth as poor growth typically leads to assumptions about the cause. More often than not, it’s wrongly assumed that baby is not eating enough or a nursing mother is not producing enough breastmilk. Poor advice to make baby eat more or increase milk supply follows. And this has the potential to cause a gamut of infant feeding problems, gastro-intestinal problems, and feeding-related growth problems. See growth mistakes for more.

Written by Rowena Bennett.