Understanding Prader-Willi Syndrome
In recognition of Eunice Kennedy Shriver, whose boundless vision advanced the progress of people with disabilities for generations, in appreciation for her special interest in this project and the generous contribution of the Joseph P. Kennedy, Jr. Foundation toward the funding and support of this booklet.

Overview of Prader-Willi Syndrome

This booklet offers information for expectant parents first learning about Prader-Willi syndrome (PWS), which is a genetic condition. Chromosomes are tiny, but very important, structures in every cell. Chromosomes contain the genes that give instructions for our bodies to grow and function. Most people are born with 46 chromosomes in their cells, 23 from their mother and 23 from their father to make a total of 23 matched pairs.

Therefore, each person usually has two copies of chromosome 15, one from the mother and one from the father. PWS occurs when part of one chromosome 15 is changed, missing, or turned off. About one out of every 15,000-25,000 babies is born with this condition. PWS occurs equally among males and females and also different races. [1]

The range and severity of symptoms can vary widely for people with PWS. Therefore, each person with this condition has his or her own strengths and challenges that no one can predict before birth.

In general, most people with PWS have mild to moderate intellectual disabilities. PWS can also cause different behavioral and health issues. Another issue for most people with PWS is weight management. Most babies with this condition have low muscle tone and struggle to eat and gain weight at first. Later, they begin to have an overactive appetite beginning between the ages of 3 and 8 years. They need help throughout their lives to avoid overeating and gaining too much weight. Without effective management, excessive weight gain and obesity can be life-threatening. [1] Most people with PWS also have puberty and fertility issues.

While people with PWS do face challenges, health care, education, research, and public attitudes have greatly improved their lives. This progress has given them more opportunities as valued members of their families and communities. Food and exercise management, as well as growth hormone therapy starting in infancy, also improve health outcomes for people with PWS. This means that more people with PWS are finishing school, finding jobs, and living healthier lives. [1]

More information about PWS can be obtained from health and genetics professionals. National and local PWS organizations can also offer support. These resources can be helpful when looking for a range of views on living with this condition.

  1. McCandless SE and The Committee on Genetics. Clinical Report- Health Supervision for Children with Prader-Willi Syndrome., Pediatrics 2011;127;195-204

Genetic Screening and Testing

Understanding Prenatal Issues

If a pregnant woman wants to know whether or not the baby has PWS, she must have either a chorionic villus sampling (CVS) or amniocentesis (tests that take samples of fetal tissue or fluid). Prenatal diagnosis of PWS is possible via special tests performed on the fetal cells obtained from the CVS or amniocentesis. Any reproductive decisions related to this diagnosis should only be made after a diagnosis of PWS from a CVS or an amniocentesis.[1] A genetics expert can give advice about the best diagnostic test for each patient.

A pregnant woman may be offered a screening test during pregnancy called cell-free DNA (cfDNA) that can include PWS. Although screening for PWS may be available via cell-free DNA, the American College of Obstetricians and Gynecologists (ACOG) does not recommend this test for PWS because of the high chance for error resulting in false negative and false positive results.[1] Screening tests are not recommended for patients with a family history of PWS. Instead, diagnostic testing should be done if prenatal diagnosis of PWS is desired. During pregnancy, there are also no ultrasound findings to suspect PWS.

Pregnant women who consider prenatal testing for PWS should talk to their obstetric provider. Patients may want information for various reasons. Some might use prenatal test results to prepare and learn more about the condition. Some might use a confirmed prenatal diagnosis to consider pregnancy management decisions. For all of these personal concerns, obstetricians and medical genetics professionals can provide referrals to specialists, discuss pregnancy management, and give patients more information. They can share valuable knowledge about PWS and can also help patients consider how their personal views, values, and beliefs affect their decision-making.

Explaining Test Results

The medical professionals who can explain genetic testing and the results might include any of the following with genetics expertise: medical geneticists, genetic counselors, neonatologists, pediatricians, obstetricians, maternal-fetal medicine specialists, or family medicine providers. In some areas, nurse practitioners, midwives, or physician assistants may also be involved.

Receiving news about a diagnosis can feel overwhelming, and families often cope with a range of emotions during this time. The chromosome changes that cause PWS are present from the time of conception and usually happen by chance. This condition is not caused by anything the parents did or did not do before or during pregnancy. If there is a family member with PWS, the chances of recurrence depend on the genetic change that caused PWS in the family member and how people are related. In this case, anyone with a family history of PWS should be referred to a medical genetics expert.

Genetic counselors and medical geneticists can be found by getting a referral from a physician or by searching online at the National Society for Genetic Counselors or the American College of Medical Genetics and Genomics.

For more specific information about the genetics of PWS, please refer to the following resource:

GeneReviews® [2]

  1. ACOG practice bulletin number 163: screening for fetal aneuploidy. Obstet Gynecol 2016;127:e123–137.

  2. Driscoll DJ, Miller JL, Schwartz S, et al. Prader-Willi Syndrome. 1998 Oct 6 [Updated 2017 Dec 14]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2019.

Medical Issues

Children with PWS are more likely to have certain medical conditions. However, earlier diagnosis, better healthcare, food management, weight control, and hormone treatment can help people with PWS live longer, healthier lives.[1]

Almost all newborns with PWS have low muscle tone and difficulty feeding. This may require special bottles or a nasogastric tube (feeding tube through the nose) to help with feeding during the first few weeks of life. Between 3-8 years old, children with PWS start to develop an overactive appetite for food (hyperphagia). In addition, as they get older, children with PWS no longer feel full the way people usually do when they overeat. This can lead to obesity if not managed properly. People with PWS need help to manage their eating habits because obesity is a significant health concern for people with PWS as they age. The health issues caused by obesity can include Type II diabetes, difficulty breathing during sleep (sleep apnea), and heart failure. People with PWS can avoid these health issues and live longer lives with strict food intake management.[2]

Other possible health issues include scoliosis (curving of the spine), a high pain threshold, infertility, and hypogonadism (undescended testes or a small penis in males or a small clitoris in females). A typical person with PWS usually has some of these conditions, but generally not all of them.[3] The health issues can also range in severity. This booklet shares the spectrum of issues that are tied to PWS. However, no one can predict before birth which health issues a person with PWS might have.

People with PWS need a good team of medical providers with expertise in PWS. They can help deal with these health concerns unique to PWS. Some specialists on the team may include a lung specialist (pulmonologist), digestive specialist (gastroenterologist), nutritionist, geneticist, developmental pediatrician, and growth hormone specialist (endocrinologist).[3]

Although some people with PWS do not produce enough growth hormone, studies show that providing growth hormone treatments can help most children with PWS. An endocrinologist can talk to families about the risks and benefits of starting on a human growth hormone (HGH) treatment plan early in life. HGH is approved by the US Food and Drug Administration for use in children with PWS. HGH treatment can help increase height and decrease body fat, while increasing energy and muscle mass. Overall, HGH can help stabilize feeding and weight gain. Some studies show it can also help with development and behavior.[3] Research is also underway to find effective drugs, devices, and therapies to further help with behavior and hunger.

For more specific information about medical issues linked with PWS, please refer to the following resources:

Health Supervision AAP
International Consensus Guidelines for HGH
Nutritional Phases in PWS

  1. Manzardo AM, Loker J, Heinemann J, Loker C, Butler MG. Survival trends from the Prader-Willi Syndrome Association (USA) 40-year mortality survey. Genet Med 2018; 20(1):24-30. doi:10.1038/gim.2017.92.

  2. Miller JL1, Lynn CH, Driscoll DC, Goldstone AP, Gold JA, Kimonis V, Dykens Am J Med Genet A. 2011 May;155A(5):1040-9.

  3. McCandless SE and The Committee on Genetics. Clinical Report- Health Supervision for Children with Prader-Willi Syndrome. Pediatrics 2011;127;195-204.


Studies of mothers and siblings show that they may experience stress when living with a child with Prader-Willi syndrome. Therefore, the whole family needs extra support in coping with daily life with PWS.[1] Some helpful sources of support are parent groups and sibling networks. Families can also get help from therapists and programs that teach coping skills for dealing with PWS. In addition, all family members need time to talk with each other about their feelings or challenges.

An earlier study showed some positive impacts for siblings of children with PWS who get the support they need. They were more willing to help others and developed a greater sense of humor. They also thought that having someone in the family with PWS brought the family closer together.[1]

Research also shows that the intelligence and daily living skills of children with PWS did not impact the life satisfaction of their parents. Life satisfaction was tied more closely to the child’s behavior and the parents’ coping styles. Parents who normally have good coping skills tend to have higher levels of life satisfaction. On the other hand, parents who normally avoid problems tend to have lower levels of life satisfaction. When parents feel stressed, they may need a program to help them develop good coping skills. Parents may also benefit from creating a PWS- specific plan of care focused on lowering stress and caring for everyone in the family.[2]

Adults with Prader-Willi syndrome most often live at home. They may also live in supervised group homes where they can get support with food intake and daily living. This setting helps adults with PWS live with more independence.

For more family resources, please refer to the following: The Sibling Support Project

For more information about government aid and savings options for people with disabilities and their families in the US, please refer to the following:

US Social Security Disability Benefits » ssa.gov
ABLE National Resource Center » ABLE RNC

  1. Mazaheri MM, Rae-Seebach RD, Preston HE, Schmidt M, Kountz-Edwards S, Field N, Cassidy S, and Packman W. The impact of Prader–Willi syndrome on the family’s quality of life and caregiving, and the unaffected siblings’ psychosocial
    adjustment. Journal of Intellectual Disability Research (2012), 57(9):861-73

  2. Tvrdik T, Mason D, Dent KM, Thornton L, Hornton SN, Viskochil DH, Stevenson DA. Stress and coping in parents of children with Prader-Willi syndrome: Assessment of the impact of a structured plan of care. Am J Med Genet A (2015) 167A(5):974-82.


People with PWS often have behavior issues beyond their intellectual disabilities and need support and treatment to cope. These behaviors may include difficulty with changes in the daily routine or temper tantrums. Other common issues include mood changes, stubbornness, and skin- picking. In addition, they may have sleep problems, obsessive and compulsive actions, and increased risk for mental health issues as teens and adults.[1]

People with PWS often need help from family members, teachers, doctors, nutritionists (food experts), and speech-language therapists to cope with some of these behaviors. Because the desire for food is so strong for people with PWS, the first step is to address behaviors that might be tied to food. Children with PWS need to learn about the value of exercise. Families also need to work with a nutritionist to develop a healthy diet at an early age. As children with PWS get older and start to feel more hungry, families, friends, and teachers will need to create a “food- secure environment.” This can mean keeping all food under lock and key, managing food access, and setting up regular meal times. A nutritionist and behavior specialist can help families create a plan. Fitness programs can also teach children with PWS the value of exercise.[1] Parent support groups can provide helpful tips and strategies to manage food related behaviors.

Counseling, positive behavior support, and speech therapy can also help children with PWS cope with behavior issues. Speech therapy can help them learn to talk about their concerns. Improved speech helps reduce their frustration as others can understand them more easily. In addition, human growth hormone (HGH) can help improve development and behavior.[2] Although people with PWS face these challenges, families report that their loved ones with PWS are caring, loving people who show perseverance and determination.[3]

For more information about how to manage behavior and set up a nutrition plan for children with PWS, please refer to the following resources:

  1. Ho AY, Dimitropoulos A. Clinical management of behavioral characteristics of Prader– Willi syndrome. Neuropsychiatric Disease and Treatment. 2010; 6:107-118.

  2. McCandless SE and The Committee on Genetics. Clinical Report- Health Supervision for Children with Prader-Willi Syndrome. Pediatrics 2011;127;195-204.

  3. The Global PWS Registry

Development and Healthcare

Children with PWS have mild to moderate intellectual disabilities or learning disabilities. These disabilities can cause developmental delays. For example, on average, a child with PWS sits at 12 months and walks at 24 months.[1] Therefore, children with PWS need extra support to meet their milestones. They also need extra help with speech.

Early Intervention is a program that offers supports and services for children with disabilities from birth to age three. These services, such as physical or speech therapy, are usually provided by each state at no cost or for a “sliding-scale” fee. Service providers work with families to teach children how to progress toward developmental milestones like crawling, walking, and speaking. Early intervention can encourage children with PWS to meet these milestones, but they often take longer than typical children.

In addition, children with PWS can usually get health coverage for their medical care under regular group health plans or state programs (Medicaid or CHIP). However, they might need more services than a typical health plan provides. To offset those extra costs, some states or regions completely cover healthcare for people with disabilities, others offer supplemental insurance programs, and some areas give little additional support.

The available healthcare and development services can vary depending on where people with PWS live. Expectant parents often find it helpful to speak with other families, local PWS organizations, pediatricians, or local government offices about the services in their area.

For more information, please also refer to the following resources:

Developmental Milestones Chart


  1. Miller JL. Approach to the Child with Prader-Willi Syndrome. J Clin Endocrinol Metab. 2012;97(11):3837-44.

Educational and Social Support

The Individuals with Disabilities Education Act (IDEA) is a federal law that gives children with disabilities, including those with PWS the right to a free and appropriate education in the public school system. After children with PWS turn three years old, they usually move from Early Intervention to pre-school services in the public school system.

Because students with PWS have mild to moderate intellectual disabilities or learning disabilities, they often receive some special education services based on their needs and strengths. Those services can include speech, occupational (motor), physical, and/or behavioral therapies. Students with PWS may receive support services while being included in a regular classroom. Most children with PWS also need extra support and a plan at school to deal with any difficult behaviors.[1]

Some educational strengths for children with Prader-Willi syndrome include a good long-term memory and strong visual memory. They also often have excellent puzzle solving and word search skills.[2]

With strong support in school, more people with PWS are completing high school and some are attending college. In addition, more adults with PWS are living semi-independently in group homes and working at different jobs,

For more information, please also refer to the following resources:

  1. Ho AY, Dimitropoulos A. Clinical management of behavioral characteristics of Prader–Willi syndrome. Neuropsychiatric Disease and Treatment. 2010;6:107-118.

  2. Verdine BN1, Troseth GL, Hodapp RM, Dykens EM. Strategies and correlates of jigsaw puzzle and visuospatial performance by persons with Prader-Willi syndrome. (2008). Am J Ment Retard. 2008 Sep;113(5):343-55. doi: 10.1352/2008.113:342-355.

PWS Resources

National PWS organizations include the Foundation for Prader-Willi Research and the Prader- Willi Syndrome Association of the USA, with chapters in each state. State chapters can share local resources and offer contacts with other families, if desired. For more information about PWS and to find local, national, and online support groups, please see the following:

For new parents or expectant parents who are preparing for the birth of a baby with Prader-Willi syndrome, please refer to the following:

  • First Steps: A Parent’s Guide to Prader-Willi Syndrome
  • Prader-Willi Syndrome: Quality of Life by Terrance N. James PhD
  • Prader-Willi Syndrome: How Parents and Professionals Struggled and Coped and Made Genetic History by John Hernandez-Storr


Parents learning about PWS should receive accurate and up-to-date resources. This information should include common life outcomes, possible medical issues and treatments, and helpful services. Expectant parents should also receive clear information about testing and pregnancy management. Together, health professionals and support groups can provide a well-rounded view of PWS.


This booklet was prepared with assistance from the Genetic Conditions Consensus Group which includes representatives of:

  • The National Society of Genetic Counselors
  • The American College of Medical Genetics and Genomics
  • The American College of Obstetricians and Gynecologists Association of University Centers on Disabilities
  • The Prader-Willi Syndrome Association of the USA
  • The Foundation for Prader-Willi Research

We would like to thank the following who offered their expertise and feedback for this resource:

  • Judith Benkendorf, MS, CGC, American College of Medical Genetics and Genomics
  • Britton Rink MD, Nationwide Children’s Hospital, Columbus, Ohio
  • Harold Kleinert, EdD, University of Kentucky
  • Beth A. Pletcher, MD, Rutgers New Jersey Medical School
  • Angela Trepanier, MS, CGC, Wayne State University
  • Mary Burr, DNP, CPNP, Prader-Willi Syndrome Association (USA)
  • Susan Hedstrom, The Foundation for Prader-Willi Research
  • Theresa Strong, PhD, The Foundation for Prader-Willi Research
  • Daniel Driscoll, MD, PhD, University of Florida
  • Meg Comeau, MHA, Center for Innovation in Social Work and Health at Boston University
  • Susan Hedstrom, The Foundation for Prader-Willi Research
  • Theresa Strong, The Foundation for Prader-Willi Research
  • Daniel Driscoll, MD, PhD, University of Florida
  • Meg Comeau, MHA

We would also like to thank all the families and individuals who participated in the photos and their generous donation of time.

We are very grateful to the Joseph P. Kennedy, Jr. Foundation for funding the development of this important resource.