Achondroplasia is a birth defect that affects a baby’s bone growth. Birth defects are health conditions that are present at birth. Birth defects change the shape or function of one or more parts of the body. They can cause problems in overall health, how the body develops, or in how the body works.
As a baby grows, a body tissue called cartilage normally becomes bone in most parts of the body. But if a baby has achondroplasia, cartilage in places like the arms and legs doesn’t turn into bone the way it should. Achondroplasia is a common cause of dwarfism (also called little people), a condition in which a person is very short (less than 4 feet 10 inches as an adult).
Achondroplasia affects about 1 in 15,000 to 1 in 40,000 babies. Most babies born with achondroplasia live a normal life span, but a few may have severe bone problems that can lead to death.
What causes achondroplasia?
A gene change (also called a mutation) causes achondroplasia. Genes are parts of your body’s cells that store instructions for the way your body grows and works. Genes are passed from parents to children. A gene change is a change to the instructions in a gene. These changes can cause birth defects and other health conditions.
Most babies with achondroplasia are born to parents who don’t have the condition. This happens when there’s a random gene change in either the egg or sperm that join together and create a baby.
If you or your partner has achondroplasia, you can pass it to your baby. If only one of you has the condition, there’s a 1 in 2 chance (50 percent) that your baby can have the condition. If both you and your partner have achondroplasia, there is:
- A 1 in 2 chance (50 percent) that your baby can have the condition
- A 1 in 4 chance (25 percent) that your baby won’t have the condition
- A 1 in 4 chance (25 percent) that your baby has the severe kind of achondroplasia that can lead to death
If you or your partner has achondroplasia or you’re the parent of a child with achondroplasia, talk to a genetic counselor about the condition. A genetic counselor is a person who is trained to help you understand about how genes, birth defects and other medical conditions run in families, and how they can affect your health and your baby's health. To find a genetic counselor, ask your provider or contact the National Society of Genetic Counselors.
How do you know if your baby has achondroplasia?
Before birth, your provider may think your baby has achondroplasia if an ultrasound shows your baby has bone problems, like shortened bones. An ultrasound uses sound waves and a computer screen to make a picture of your baby in the womb.
If the ultrasound shows these bone problems, your provider may recommend a prenatal test called amniocentesis (also called amnio) to confirm that your baby has achrondroplasia. In an amnio, your provider takes some amniotic fluid from around your baby in the uterus. The test checks for birth defects and genetic conditions in your baby.
After birth, your baby’s provider can use X-rays, a physical exam and a blood test to check your baby for achondroplasia.
What are some physical characteristics of someone with achondroplasia?
A person with achondroplasia often has:
- Short height
- Short upper arms and thighs (compared to the forearms and lower legs)
- Large head and forehead with a flat bridge of the nose
- Dental problems, including crowded or crooked teeth
- Broad, flat feet, short toes and short fingers
- Trident hand, a condition in which you have an extra space between the middle and ring fingers
- Weak muscle tone. Babies with weak muscle tone may have delays in meeting developmental milestones, like sitting, standing and walking.
- Bowed legs. This is when legs curve outward between the thighs and ankles. Bowed legs can cause pain and trouble with walking. If the bowing or pain is severe, surgery can fix bowed legs.
What health problems can achondroplasia cause and how are they treated?
People with achondroplasia can have a range of health problems, so it’s important to take your baby to see his health care provider for routine well-baby checkups.
At these checkups, your baby’s provider can compare your baby’s height, weight and head size to those of other babies with achondroplasia. This can help your baby’s provider spot and treat some problems early on.
People with achondroplasia often have these health problems:
- Apnea. This is when a baby stops breathing for 15 to 20 seconds or more. Babies with apnea and other breathing problems may need surgery to remove the tonsils and adenoids (lymph tissue near the throat).
- Repeat ear infections. Some babies with achondroplasia need ear tubes. These are small tubes placed in the ear that let air into the middle ear and help lower chances of ear infections. Without treatment, repeat ear infections can cause hearing loss.
- Obesity (being very overweight). Healthy eating and being active can help your child stay at a healthy weight as she grows.
- Compression of the upper end of the spinal cord. This is when the opening where the head and spine (backbone) connect is too small. The spinal cord gets squeezed (compressed), causing trouble with breathing. A small number of babies with achondroplasia die suddenly (often during sleep) from compression. If needed, surgery can widen the opening to ease pressure on the spinal cord.
- Spinal stenosis. Spinal stenosis causes the spine to narrow, putting pressure on the nerves and spinal cord. This can cause low back pain, problems with urination and weakness, tingling and pain in the legs. Symptoms usually appear when a person with achondroplasia is a teen or adult. Surgery can ease pressure on the spinal cord.
- Hydrocephalus (fluid buildup in the brain). Your baby’s provider measures your baby’s head at regular checkups to help catch hydrocephalus early. In some cases, a surgeon needs to drain the extra fluid from a baby’s brain.
- Kyphosis (a small hump in the upper back). A baby may have kyphosis due to poor muscle tone, but it usually goes away after she starts walking. Strollers or carriers that don’t give good back support can make kyphosis worse. If your child stills has kyphosis after she starts walking, she may need a back brace or surgery to correct it.
- Lordosis (inward curving of the lower back). This can develop after your child starts walking and can lead to waddling. Special exercises or physical therapy can help.
Little People of America (LPA)
Human Growth Foundation
The Magic Foundation for Children’s Growth and Related Adult Disorders
Last reviewed April 2013
Frequently Asked Questions
Can dad's exposure to chemicals harm his future kids?
Dad's exposure to harmful chemicals and substances before conception or during his partner's pregnancy can affect his children. Harmful exposures can include drugs (prescription, over-the-counter and illegal drugs), alcohol, cigarettes, cigarette smoke, chemotherapy and radiation. They also include exposure to lead, mercury and pesticides.
Unlike mom's exposures, dad's exposures do not appear to cause birth defects. They can, however, damage a man's sperm quality, causing fertility problems and miscarriage. Some exposures may cause genetic changes in sperm that may increase the risk of childhood cancer. Cancer treatments, like chemotherapy and radiation, can seriously alter sperm, at least for a few months post treatment. Some men choose to bank their sperm to preserve its integrity before they receive treatment. If you have a question about a specific exposure, contact the Organization of Teratology Information Specialists at www.otispregnancy.org.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
Does cleft lip or cleft palate cause dental problems?
A cleft lip or cleft palate that extends into the upper gums (where top teeth develop) can cause your baby to have certain dental problems, including:
- Missing teeth
- Too many teeth
- Oddly shaped teeth
- Teeth that are out of position around the cleft
Every baby with a cleft lip or palate should get regular dental checkups by a dentist with experience taking care of children with oral clefts. Dental problems caused by cleft lip or palate usually can be fixed. If needed, your baby can get ongoing care by a team of experts, including:
- A dentist
- An orthodontist to move teeth using braces
- An oral surgeon to reposition parts of the upper jaw, if needed, and to fix the cleft
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause ear problems?
Cleft lip does not cause ear problems.
Babies with cleft palate, however, are more likely than other babies to have ear infections and, in some cases, hearing loss. This is because cleft palate can cause fluid to build up in your baby’s middle ear. The fluid can become infected and cause fever and earache. If fluid keeps building up with or without infection, it can cause mild to moderate hearing loss.
Without treatment , hearing loss can affect your baby’s language development and may become permanent.
With the right care, this kind of hearing loss is usually temporary. Your baby’s provider may recommend:
- Having your baby’s ears checked regularly for fluid buildup
- Medicines for treating fluid buildup and ear infections
- Ear tubes if your baby has fluid in his ears over and over again. Ear tubes are tiny tubes that are inserted into the eardrum to drain the fluid and help prevent infections.
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause problems with breastfeeding?
Babies with only a cleft lip usually don’t have trouble breastfeeding. Most of the time, they can breastfeed just fine. But they may need some extra time to get started.
Babies with cleft lip and palate or with isolated cleft palate can have:
- Trouble sucking strong enough to draw milk through a nipple
- Problems with gagging or choking
- Problems with milk coming through the nose while feeding
Most babies with cleft palate can’t feed from the breast. If your baby has cleft palate, he can still get the health benefits of breastfeeding if you feed him breast milk from a bottle. Your provider can show you how to express (pump) milk from your breasts and store breast milk.
Your baby’s provider can help you start good breastfeeding habits right after your baby is born. She may recommend:
- Special nipples and bottles that can make feeding breast milk from a bottle easier
- An obturator. This is a small plastic plate that fits into the roof of your baby’s mouth and covers the cleft opening during feeding.
See also: Cleft lip and cleft palate, Breastfeeding
Does cleft lip or cleft palate cause speech problems?
Children with cleft lip generally have normal speech. Children with cleft lip and palate or isolated cleft palate may:
- Develop speech more slowly
- Have a nasal sound when speaking
- Have trouble making certain sounds
Most children can develop normal speech after having cleft palate repair. However, some children may need speech therapy to help develop normal speech.
See also: Cleft lip and cleft palate
What are choroid plexus cysts?
The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.
What if I didn't take folic acid before pregnancy?
If you didn’t take folic acid before getting pregnant, it doesn't necessarily mean that your baby will be born with birth defects. If women of childbearing age take 400 micrograms of folic acid every day before and during early pregnancy, it may help reduce their baby’s risk for birth defects of the brain and spin called neural tube defects (NTDs). But it only works if you take it before getting pregnant and during the first few weeks of pregnancy, often before you may even know you’re pregnant.
Because nearly half of all pregnancies in the United States are unplanned, it's important that all women of childbearing age (even if they're not trying to get pregnant) get at least 400 micrograms of folic acid every day. Take a multivitamin with folic acid before pregnancy. During pregnancy, switch to a prenatal vitamin, which should have 600 micrograms of folic acid.
Last reviewed November 2012