Skeletal dysplasias are a group of conditions that involve the unexpected growth and development of the baby’s bones. These conditions affect the fetal skeleton as it develops in the mother’s womb.

There are many different types of skeletal dysplasias. Some are more serious than others. Severe skeletal dysplasias are the most serious types of these conditions.

If your baby has a severe skeletal dysplasia, there is very limited bone growth and the bones in the chest (ribs) may not grow properly. This means that the lungs may not fully develop because the chest is too small. Sadly, most babies with a severe skeletal dysplasia will be stillborn or die soon after birth. There is no way to stop or cure a severe skeletal dysplasia.

Causes

There are around 350 different types of skeletal dysplasias and there can be many causes. It is not caused by something you have or have not done.

Generally, however, the causes can be cataloged into three groups:

• Genetically inherited as dominant or recessive traits or X-linked disorders
• The result of spontaneous mutations
• Secondary to exposure to a toxic substance or infectious agent that results in the disruption of normal skeletal development 

Nearly half of the documented skeletal dysplasias are caused by a genetic mutation that makes prenatal diagnosis possible through genetic testing.

Severe skeletal dysplasias happen in about one baby out of every 10,000 (0.01%).

How we find severe skeletal dysplasias

We screen for severe skeletal dysplasias at the 20-week screening scan (between 18+0 and 20+6 weeks of pregnancy). Sometimes these conditions may be visible during an earlier scan, usually around 12 weeks of pregnancy.

Follow-up tests and appointments

As the result of your 20-week screening scan suggests your baby may have a severe skeletal dysplasia, we will refer you to a specialist fetal medicine team for further investigation, support and counselling. They may be based at the hospital where you are currently receiving antenatal care, or in a different hospital.

The fetal medicine team will offer you more scans and extra tests, such as amniocentesis, which will confirm if your baby has a severe skeletal dysplasia and what this might mean. You may also be referred to a genetics team and offered further tests to find out what type of severe skeletal dysplasia your baby has. Usually, the exact diagnosis is made through genetic testing, X-rays and a detailed examination after your baby is born.

It may be useful to write down any questions that you want to ask before you see the specialist team.

Some examples of skeletal dysplasias

Common skeletal dysplasias and associated symptoms include:

• Thanatophoric dysplasia is typically characterised by abnormal shortness of limbs; a bowed femur (thigh bone) or other bones of the extremities; a small chest cage; thickened soft tissues; flattened vertebrae; unusually prominent forehead and depressed nasal bridge; and Cloverleaf skull (type II).
• Campomelic dysplasia is generally associated with a bowed femur (thigh bone) or other bones of the extremities; shortened limbs clubfeet; missing ribs; ambiguous genitalia; flattened facial features; and an unusually prominent forehead.
• Achondroplasia is characterised by shortened limbs, short forearms and lower legs; stubby fingers unusually prominent forehead; and abnormally decreased distance of the lumbar vertebrae in the lower back.
• Osteogenesis imperfecta typically includes fractures; bowed, irregular thickened bones; short/normal size extremities; soft, thin skull
• Achondrogenesis presents with thickened soft tissues; short limbs; bones of the spine that are not mineralised or fully formed; and a small thorax.

Outcome

There is no treatment for severe skeletal dysplasias. Sadly, most babies with a severe skeletal dysplasia will be stillborn or die soon after birth. This is because they cannot survive without properly developed lungs.

Next steps and choices

If it is confirmed that your baby has a severe skeletal dysplasia, you can talk to the specialist team caring for you during your pregnancy about your baby’s condition and what this might mean. The team will provide you with as much information as possible so you can make a personal informed choice about your pregnancy options. These include either continuing with your pregnancy or ending your pregnancy.

You might want to learn more about severe skeletal dysplasias. It can be helpful to speak to a support organisation with experience of helping parents in this situation.

If you decide to continue with your pregnancy, the specialist team will help you plan your care. They will discuss with you how you wish your baby to be cared for after birth. Depending on your baby’s specific symptoms, palliative care may be offered. Children’s palliative care is about promoting the best possible quality of life and care for every child with a life-limiting condition and their family.

If you decide to end your pregnancy, you will be given information about what this involves and how you will be supported. You should be offered a choice of where and how to end your pregnancy and be given support that is individual to you and your family.

If you wish to build some memories of your baby, staff will offer you and your family help to do so.

Only you know what the best decision for you and your family is. Whatever decision you make, your healthcare professionals will support you.

Future pregnancies

Depending on the type of severe skeletal dysplasia your baby has, there may be a chance of having another baby with this condition. However most parents go on to have a healthy baby who is not affected by skeletal dysplasia.

You will be referred to a genetic counsellor or clinical geneticist to discuss future pregnancies.

More information

Antenatal Results and Choices (ARC) is a national charity that supports people making decisions about screening and diagnosis and whether or not to continue a pregnancy.

Stillbirth and neonatal death charity (Sands) is a national charity that supports anyone affected by the death of a baby.

Together for shorter lives is a national charity that makes sure seriously ill children and their families make the most of every moment they have together, whether that’s years, months or only hours.