Chromosomal and Genetic Conditions

Conjoined Twins

What are conjoined twins?

When twins are born with their bodies connected, they are called conjoined twins. Some twins share only a small amount of tissue, and both children may have all the organs and other structures they need.

Usually, the connection is more complex. In some cases, children may share:

  • Vital organs, like 1 heart
  • Many structures, like several parts of the digestive, genital and urinary systems
  • A large portion of the body, like all of the lower body
  • Part of the brain and skull

  • Conjoined twins begin as a single fertilized egg. Sometimes a single egg splits in half to create 2 separate identical twins. Usually this happens about 2 weeks after the egg is fertilized.

    There are 2 ideas about what causes conjoined twinning:

    1. The egg divides late and does not divide all the way.
    2. The egg divides but then joins back together.

Outlook for Conjoined Twins

More conjoined twins survive now than in the past. This is a result of advances in imaging studies, surgical techniques and anesthesia. Even so, about 40% of conjoined twins are not alive when they are born. About 35% die within a day after they are born because their organs cannot support them.

Our treatment goal is to give both children the best chance for a good quality of life. Sometimes surgery to separate the twins is the best option. The success of the separation surgery depends on many factors, mainly where the twins are connected and which structures they share. Often, both twins survive. But sometimes 1 or both die, usually because of a serious birth defect.

Sometimes separation surgery is not possible. Some conjoined twins have happy, healthy, full lives by staying connected.

Conjoined Twins at Seattle Children’s

Seattle Children’s is 1 of the nation’s most experienced hospitals in treating conjoined twins. Care starts during pregnancy, as we monitor your twins’ health, learn as much as we can about their condition and plan for their care after birth. We help you understand all your options so you can make the choices that are best for your family. Our team has the knowledge, experience and facilities to:

  • Determine which treatment is likely to give your babies the best quality of life
  • Perform surgery to successfully separate your twins
  • Provide care for your conjoined twins if they cannot be separated or your family decides not to separate them

Read about Kathleen and Charity, separated at Seattle Children’s in 2000:

If you would like an appointment, talk with your pregnancy care provider for a referral to our Prenatal Diagnosis and Treatment Program. If you would like more information or have a referral, call 206-987-5629 to schedule an appointment.

    • Usually, parents find that their twins are conjoined when the mother has an ultrasound during pregnancy. Our Prenatal Diagnosis and Treatment team will do a detailed evaluation. We provide information and compassionate support to guide you in finding the care that is right for your family.
    • Advanced imaging studies during pregnancy help us learn as much as we can about your twins’ condition and how best to treat them.
    • Careful coordination with your birth hospital helps plan for the special care your babies will need at birth and as they travel by ambulance to Seattle Children’s.
    • Our transport team of physicians, nurses and respiratory therapists are national leaders in safely moving fragile newborns.
    • We are skilled and equipped to care for the sickest newborns. Our Level IV Neonatal Intensive Care Unit (NICU) provides the highest level of care.

    • Each set of conjoined twins is unique. An expert team of healthcare providers will assess your twins’ condition and plan and carry out their treatment. Your children’s team will include nurses, surgeons and doctors who specialize in newborns with complex problems (neonatologists). Other specialists as needed will care for your child. These may include cardiologists, lung specialists, anesthesiologists, urologists, orthopedic surgeons, plastic surgeons, neurosurgeons, cardiac surgeons, physical therapists, occupational therapists and nutritionists.
    • We talk with you about what to expect, the babies’ chance for survival, whether it will be possible to separate them and their likely quality of life if they stay connected or are separated.
    • Seattle Children’s is a leading center in successful surgery for conjoined twins. Even so, surgery is not always the best choice. We work with you to decide on the best treatment for your babies.
    • Whether your twins are separated or remain joined, we provide complete care through childhood and into the early adult years. We have all the experts your family needs.
    • Seattle Children’s ranks among the best in all 10 pediatric specialties rated by U.S. News & World Report in 2018. We are the only hospital in the Northwest to do so.

    • We know how challenging and scary it can be to find a medical problem during pregnancy. Your family has a full team behind you, including doctors, nurses, lactation specialists and social workers.
    • We help you fully understand your treatment options and make the choices that are right for your family. We connect you to community resources and support groups.
    • At Seattle Children’s, we work with many children and families from around the Northwest and beyond. We can help with financial counseling, schooling for other children in the family, housing, transportation, interpreter services and spiritual care. Learn about our services for patients and families.

    Read about Kevin Mick, who was born a conjoined twin in 1992, and is now living a healthy, active life.

Conjoined Twins: Types and Symptoms

Conjoined twins may be connected to each other in many different ways. Their health and any symptoms depend on:

  • How each baby developed.
  • Which structures they share.
  • How well their organs work.
  • Their lung development. Conjoined twins are usually born early and may have breathing problems.

Doctors group conjoined twins into the following categories based on where they are joined.

  • This is the most common type, accounting for 40% of conjoined twins. The twins are face to face. This type is called thoracopagus (pronounced thor-uh-KOP-uh-gus).

    In about 75% of cases, the twins share a heart. Twins joined at the chest may also share a liver, biliary tract (which carries bile) and upper digestive tract (esophagus, stomach and small intestine).

  • These twins are also face to face. This type is called omphalopagus (pronounced om-fuh-LOP-uh-gus) or xiphopagus (pronounced zy-FOP-a-gus). The twins may share a liver, biliary tract and upper digestive tract. About 34% of conjoined twins are in this group.

  • These twins are back to back. This type is called pygopagus (pronounced pie-GOP-uh-gus). The twins may share part of the lower digestive tract (large intestine, rectum and anus) and part of the skeleton, nervous system and genitals. About 18% of conjoined twins are in this group.

  • Usually, these twins partly face each other. But they may be oriented to each other in different ways. They may share a liver and biliary tract, part of the upper and all of the lower digestive tract, the genital and urinary systems and part of the skeleton. About 6% of conjoined twins are in this group. This type includes ischiopagus (pronounced is-kee-OP-uh-gus) and pygopagus twins.

  • These conjoined twins may share a skull, brain and other parts of the nervous system. This type is called craniopagus (pronounced kray-nee-OP-uh-gus). About 2% of conjoined twins are in this group.

Diagnosing Conjoined Twins

  • In most cases, doctors see that twins are conjoined during a routine ultrasound late in the first trimester of pregnancy or in the second trimester. Experts at Seattle Children’s Prenatal Diagnosis and Treatment Program will do imaging studies to learn more about your babies’ conditions. We explain what the images show and which structures your twins may share.

    These studies may include:

    • Ultrasound
    • Echocardiography
    • Prenatal MRI (magnetic resonance imaging)

    Seattle Children’s doctors who care for conjoined twins will talk with you about what to expect, including whether separation is possible. Some parents continue their pregnancy. Others decide to end their pregnancy.

    If the pregnancy continues, we will carefully monitor your babies’ conditions. This helps you and your healthcare team prepare for the diagnostic tests and treatments the twins will need once they are born. We arrange for the safe transfer of your babies to Seattle Children’s soon after they are born.

  • Usually delivery by cesarean section (C-section) will be scheduled a month before the twins’ due date. This is because a vaginal birth is too hard for the mother and babies. We recommend delivery of your baby at the University of Washington by obstetricians who are experienced with high-risk pregnancies. Your babies will transfer to Seattle Children’s soon after birth. Our transport team is very experienced bringing fragile newborns from their birth hospitals to Seattle Children’s.

    We have the expertise to do these and other tests to learn more about your conjoined twins’ condition:

    • Arteriography to see inside blood vessels (arteries) using x-rays and special dye
    • Echocardiography to see how well the heart muscle is working
    • Electrocardiography to study heart rate and rhythm
    • Ultrasound to make pictures of organs and structures inside the body using sound waves
    • CT (computed tomography) scan, using computers and X-rays to make pictures inside the body
    • MRI (magnetic resonance imaging), which avoids the radiation used in CT scans

    These tests give our healthcare team important information about your babies’ health and how they are connected. This will help you and the healthcare team decide how to care for the twins.

Treating Conjoined Twins

At Seattle Children’s, your babies will get care from a whole team of experts in our Level IV Neonatal Intensive Care Unit (NICU). Our NICU provides the highest level of care, including state-of-the-art support for breathing.

Your babies’ treatment will depend on the health of each twin and how they are joined.

  • Treatment for each set of twins is unique. The connection between the twins’ bodies may range from fairly simple to very complex.

    • Both children may have all the organs and other structures they need.
    • They may share some structures or vital organs, like a heart. It may not be possible to separate the twins in all cases.
    • Their bodies may be able to support both their lives, or it may be hard for 1 or both to survive because of health problems.

    Your twins’ healthcare team will do tests during pregnancy and after birth to learn as much as they can about your babies’ anatomies and how well their bodies are working. The team uses this information to create a detailed treatment plan. Our goal is to give both children the best chance for a good quality of life, whenever possible.

  • Whether to do surgery to separate your twins depends on their chance of survival and quality of life for each baby.

    Sometimes separation surgery is not possible for a variety of reasons, so staying connected is the only real option. Some conjoined twins have happy, healthy, full lives by staying connected.

    Surgery may be the best option:

    • For the physical health of both children, while also giving them the chance to have independent bodies and lives
    • Because 1 twin cannot survive because of a severe birth defect and separation is the only way to give the other twin a chance to live

    Usually, twins have separation surgery in the first 3 months to 12 months of life. The success of the separation surgery depends on many factors, mainly where the twins are connected and which structures they share.

    Your healthcare team will speak with you about what your twins’ lives may be like whether they are joined or separated. They will help you consider which option is best for your twins.

  • As we plan and prepare for surgery, your twins will get care from many different types of experts. They will work together to plan the steps and timing of the surgery and the care your children will need before and after. One doctor will oversee the team and coordinate all parts of the plan.

    In most cases, doctors will do the separation surgery after your twins are at least 3 months old. This allows time for:

    • The many imaging studies and other tests that might be needed to learn about your twins’ bodies.
    • Any procedures your babies may need to prepare them for separation.
    • The babies’ bodies to grow and get stronger. This makes it easier for doctors to do the surgery and easier for the twins to withstand the surgery.

    In some cases, conjoined twins need to be separated before they are 3 months old because of a health emergency or a problem that cannot wait.

    Two complete teams work together very closely to separate twins. Each team includes surgeons, anesthesiologists and nurses.

  • Whether they stay connected or are separated, your twins will need long-term follow-up visits during childhood and into their early adult years. The healthcare team will check your children’s growth and development. We care for any long-term medical issues they might have.

    Follow-up care will depend on the type of conjoined twins they are and other health issues they may have. Seattle Children’s has a broad range of specialty clinics and programs to meet their needs, including:

    • Surgical Pulmonary Follow-up
    • Reconstructive Pelvic Medicine
    • Pediatric General and Thoracic Surgery
    • Cardiology
    • Nephrology
    • Orthopedics
    • Neurodevelopmental
    • Adolescent gynecology
    • Urology
    • Physical therapy and occupational therapy
    • Nutrition

Contact Us

If you have questions about prenatal diagnosis or treatment options for conjoined twins, call our Prenatal Diagnosis and Treatment Program at 206-987-5629.

Providers: see how to refer a patient.