Slow Weight Gain in Infants and Children

Slow weight gain is sometimes called “failure to thrive." It is not a disease itself, but a manifestation of many medical, social and environmental factors that prevent a child from getting the calories they need for healthy growth.

Typically, a baby’s weight doubles within their first 4 to 6 months of life and triples in their first year. For instance, a baby born weighing six pounds would typically weigh about 12 pounds by the time they were 6 months old and about 18 pounds by the time they turned 1.

Slow weight gain is not always a concern. Some infants and children are simply smaller than most other children their age. However, between 1 and 10 percent of children in the United States show delays that require some form of intervention. It is important to tell your child’s physician about any delays in your child’s growth.

Slow weight gain is a problem when it interferes with a child’s healthy development, particularly during your baby’s first year when their brain is developing.

Slow weight gain could be a problem if:

• Your newborn doesn’t regain their birth weight within 10 to 14 days after their birth
• Your baby up to 3 months old gains less than an ounce a day
• Your infant between 3 and 6 months gains less than 0.67 ounces a day
• Your child of any age has been growing steadily and suddenly stops growing

Although you should always discuss slow weight gain with your child’s doctor, it is less of a concern when:

• Your newborn wakes up on their own and wants to feed 8 to 12 times a day
• Your baby is growing at a steady rate
• Your baby has about the same number of wet and dirty diapers as other babies

One of the most obvious symptoms of slow weight gain is size: your child is much smaller than other children their age. This may include weight, height and size of their head.

If your baby is not getting enough calories, you may notice the following symptoms:

• Lost interest in the world around them
• Extreme sleepiness
• Frequent crying and fussiness
• Missed physical milestones: not rolling over, sitting up or walking at the same time as other kids their age

Several possible factors can cause slow weight gain, from a medical condition to social or financial hardship. Anything that interferes with a child’s access to food or ability to digest food can impair their growth. Often it is caused by a combination of factors.

Medical causes:

• Premature birth can make it hard for your child to feed until the muscles they use to suck and swallow fully develop.
• Down syndrome can also interfere with a child’s ability to suck and swallow.
• Metabolic disorders like hypoglycemia, galactosemia or phenylketonuria can interfere with the body’s ability to convert food into energy.
• Cystic fibrosis can prevent a child from absorbing calories.
• A food allergy or food intolerance may limit what foods your child can eat without feeling ill.
• Gastroesophageal reflux can cause your child to vomit frequently.
• Anything that causes chronic diarrhea can prevent your child from receiving enough nutrition.

Social and financial causes:

• Parents may not prepare formula correctly or understand how often their infant or child needs to eat.
• Household stress from divorce, death or another disruption can cause a child to stop eating.
• Poverty may make it hard for parents to provide enough food for their children.

Since slow weight gain is not a specific condition but the result of other factors, your child’s doctor will focus on discovering the underlying cause. Diagnosis typically starts with a full medical history and physical exam. The doctor will also review your child’s pattern of weight gain in relation to the standard growth curves.

Screening tests may include a blood count, screening studies for celiac disease, thyroid hormones, serum electrolytes and urinalysis.

Treatment depends on what is preventing a child from gaining weight. If the cause is an underlying medical condition, your child’s doctor may focus on treating that condition.

If poor nutrition is contributing to your child’s slow weight gain, a nutritionist may work with you to develop a plan for providing your child a well-balanced diet.

If your child has trouble chewing or swallowing, a speech pathologist will provide strategies to develop the necessary muscles.

If your child seems healthy but refuses to eat, a behavioral psychologist may be able to help your child and you work through issues that lead to this behavior.

Depending on your child’s age and underlying medical condition, more aggressive forms of nutritional support, such as a feeding tube may be necessary. This intervention may be temporary until your child develops healthy eating habits that support their growth and development.

The Growth and Nutrition Program at Boston Children's Hospital is a multidisciplinary program of doctors, nurses, dietitians, social workers, behavioral specialists and speech therapists who will work together to determine the causes and treatment for slow weight gain for your child. We work in partnership with parents, primary care providers, and staff from other disciplines across the hospital to develop an individual long-term treatment plan for each child and address the factors affecting their growth.

If your child’s gain in height is the primary concern, not their weight gain, we may refer your child to the specialists in Division of Endocrinology.