Slow Weight Gain in Infants and Children

  • Overview

    Slow weight gain is sometimes called “failure to thrive." It is not in itself a disease, but rather is a manifestation of medical, social, and/or environmental factors that may prevent a child from getting the calories he or she needs to maintain a healthy rate of growth. Over the next few pages we will introduce you to the basics of slow weight gain, its potential causes, and how the physicians and the other team members of the Growth and Nutrition Program at Children’s Hospital Boston address it.

    Between one and 10 percent of children in the United States show delays in weight gain compared to their peers that do require some form of intervention.

    How Children’s Hospital Boston approaches slow weight gain

    The Growth and Nutrition Program believes that the best approach to a child whose growth has slowed is to have a group of specialists with complementary backgrounds (i.e., gastroenterology, pediatrics, nutrition, feeding & swallowing, behavioral psychology, social work, nursing) working together to determine the causes and treatment for the slow weight gain. Our multidisciplinary team works 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 to make sure that the factors affecting his or her growth is addressed.

    If the main concern is about the child’s gain in height, rather than weight gain, the patient may be referred to the specialists in Children’s Department of Endocrinology.

    Slow weight gain: Reviewed by Susanna Y. Huh, MD, MPH
    © Children’s Hospital Boston, 2012

    Children's Hospital Boston
    333 Longwood Avenue, 5th floor 
    Boston, MA 02115


  • We understand that you may have a lot of questions when your child is diagnosed with slow or delayed weight gain.
    • How do you define it?
    • What could be contributing to my child’s slow weight gain?
    • What are the recommended courses of action?
    • What are the potential consequences of delays in weight gain?

    We’ve tried to provide some answers to those questions here.  When you and your child meet with our experts, they will explain your child’s condition and the recommended options more fully.

    What defines normal weight gain?

    Growth Curve Genetic

    A growth curve for a child whose growth followed one pattern for the first four months of life and then shifted to a new pattern. This pattern can be completely normal, though parents should discuss any changes in their child's rate of growth with their physician.

    growth curve undernourished

    A growth curve for a child who is undernourished.

    A child’s weight and height generally track in a fairly consistent fashion over time, albeit with some fluctuation. This pattern can be described as a percentile on a growth curve. By plotting a child’s weight or height (length in the case of an infant or toddler) over time, a growth curve demonstrates their pattern of growth. Health care providers generally use one of two sets of growth curves to monitor a child’s growth. The World Health Organization (WHO) curve is recommended for children less than two years of age. The U.S. Centers for Disease Control and Prevention (CDC) curve is recommended for children over the age of two. The growth of children with certain known conditions (e.g., a genetic syndrome such as Down syndrome) is best monitored using growth curves developed specifically for those conditions.

    Children generally gain weight in proportion to their age and height or length. What is more important than a child’s position on a growth curve (e.g., 25th percentile, 50th percentile, 90th percentile) is his or her pattern of growth. So for instance, a two-year-old boy whose weight has consistently been and continues to be at the 15th percentile for his age is displaying a normal pattern of weight gain.

    Sometimes, normal children may grow at a given rate for a certain period of time, followed by a somewhat different rate of growth for another period of time. For example, a two-year-old girl may chart a weight at the 25th percentile for the first year of life, then at the 15th percentile for the second year of life; if there are no worrisome factors, this could be considered a normal pattern of weight gain. Your physician should evaluate any change in your child’s pattern of weight gain to determine whether it falls within the range of normal.


    What could cause a child to gain weight slowly?

    There is a range of possible reasons for why a child might gain weight slowly, and often more than one reason is contributing at a time. Any factors that affect a child’s access to food – be they medical, social, economic, etc. – can affect weight gain. Medically, anything that causes the following could be a contributing factor:

    • Inadequate food intake
    • Problems with digestion or absorption of food or absorption
    • Increased metabolism

    Children born prematurely (before their due date) are at particularly high risk for delays in weight gain. Also, for some children – those with small parents, for instance – relatively slow weight gain may be normal.

    Parents should always discuss a slow rate of weight gain with their physician.

    Signs and symptoms

    What defines slow weight gain?

    As noted above, health care providers expect to see a child maintain a stable pattern of growth – that is, growth that consistently follows a particular weight-for-age or weight-for-height percentile. If the pattern changes significantly, concerns can arise.

    A child’s weight gain raises concern when:

    1.     Their weight or weight-for-height is two or more standard deviations below the mean for their gender and age; or

    2.     Their weight curve has crossed downward by more than two major percentile lines on the CDC or WHO growth curves after having previously achieved a stable pattern of growth.

    As noted above, some healthy children may achieve a stable pattern of growth and have their growth slow such that they continue on another curve. Any change in pattern should be discussed with your child’s physician.

    How is slow weight gain diagnosed?

    Medical history family history, and physical examination are critical in finding the reason(s) for your child’s slow weight gain. Carefully chosen laboratory tests and other diagnostic studies can also provide valuable information.

    For details, see Tests.

    What can be done in cases of slow weight gain?

    We work with your family and your child’s primary care provider to develop a comprehensive, long-term plan aimed at improving your child’s weight gain.

    For details, see Treatment & Care.

    How can slow weight gain affect my child in the long term?

    The outlook for a child with slow weight gain depends on the timing and severity of the issue, as well as on the presence of any underlying disease. In addition, your child’s genetic potential for growth can also have an effect.

    Questions to ask your doctor

    You and your family play an essential role in addressing your child’s growth. It’s important that you share your observations and ideas with your child’s treating providers, and that you have all the information you need to fully understand the treatment team’s explanations and recommendations.

    You may have many questions about your child’s growth. It’s often very helpful to jot down your thoughts and questions ahead of time and bring them with you, along with a notebook, to your child’s appointment. That way, you’ll have all of your questions in front of you when you meet with your child’s treating providers and can make notes to take home with you.

    Some questions to ask your doctor might include:

    • What is causing my child's slow weight gain and how was this diagnosis arrived at?
    • Are there any other conditions my child might have instead?
    • Does my child need further testing?
    • What is the long-term outlook for my child?
    • Are there medications that will be prescribed and do they have potential side effects?
    • How should I talk to my child and other concerned family members about this condition and the potential impact upon his or her long-term health?
    • Do I need to make any changes to my child’s home and school routines?
    • Can you point me to educational and support service resources for children with slow weight gain in my area?
    • What other resources can you direct me to for more information, as well as for additional evaluations and interventions?
  • Assessing your child’s weight gain

    Physicians can gain the most information about why your child is gaining weight slowly through a combination of:

    • Physical examination
    • Medical, family, and dietary history
    • Review of your child’s pattern of weight gain in relation to the standard growth curves

    The Growth and Nutrition team will use this information to determine whether your child’s pattern of growth is of concern and to identify any contributing factors that may be impeding your child’s weight gain. For some children, this information may show that they are actually gaining weight appropriately.

    There are also some basic laboratory screening tests our team may request (e.g., a blood count, lead test, screening studies for celiac disease, thyroid hormones, serum electrolytes, urinalysis) that can provide insights into potential medical causes. We may order additional tests, such as a bone age or a barium swallow test as suggested by your child’s history and physical examination.

    Other members of our multispecialty team are likely to be included in your child’s assessment so that we can draw the most complete picture of the factors contributing to your child’s slow weight gain. For example, almost all children seen in the Growth and Nutrition Program will see a dietitian who will assess caloric intake. A speech pathologist may determine if your child has any difficulties with chewing or swallowing, and a behavioral psychologist may assess your child’s feeding environment and behaviors related to eating.

  • At Children’s Hospital Boston, we use a multidisciplinary approach to care for children with slow weight gain. After a comprehensive and focused assessment (covered above under Tests), our Growth and Nutrition Program team will work with you and your child’s primary care provider to develop a long-term plan of action.

    The first step would be to treat any underlying medical conditions. This treatment would be carried out as part of a comprehensive, multidisciplinary approach that would also include nutritional advice aimed at improving your child’s caloric intake and quality of their diet, and counseling to encourage positive mealtime behaviors.

    Should these measures prove ineffective at putting your child’s weight on a good trajectory, we would consider other, more aggressive forms of nutritional support, such as a feeding tube.

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The future of pediatrics will be forged by thinking differently, breaking paradigms and joining together in a shared vision of tackling the toughest challenges before us.”
- Sandra L. Fenwick, President and CEO