Micrognathia, or mandibular hypoplasia, is a condition in which a child has a very small lower jaw. A child with micrognathia has a lower jaw that’s much shorter or smaller than the rest of their face.

Children may be born with this problem, or it can develop later in life. It mainly occurs in children who are born with certain genetic conditions, such as trisomy 13 and progeria. It can also be the result of fetal alcohol syndrome.

In some cases, this problem goes away as the child’s jaw grows with age. In severe cases, micrognathia can cause feeding or breathing problems. It can also lead to malocclusion of the teeth, which means that your child’s teeth don’t align correctly.

Most cases of micrognathia are congenital, which means that children are born with it. Some cases of micrognathia are due to inherited disorders, but in other cases, it’s the result of genetic mutations that occur on their own and don’t pass down through families.

Here are a number of genetic syndromes that are associated with micrognathia:

Pierre Robin syndrome

Pierre Robin syndrome causes your baby’s jaw to form slowly in the womb, which results in a very small lower jaw. It also causes the baby’s tongue to fall backward into the throat, which can block the airways and make breathing difficult.

These babies may also be born with an opening in the roof of their mouth (or cleft palate). It occurs in about 1 in 8,500 to 14,000 births.

Trisomy 13 and 18

A trisomy is a genetic disorder that occurs when a baby has extra genetic material: three chromosomes instead of the normal two. A trisomy causes severe mental deficiencies and physical deformities.

According to the National Library of Medicine, about 1 in every 16,000 babies has trisomy 13, also known as Patau syndrome.

According to the Trisomy 18 Foundation, around 1 in 6,000 babies has trisomy 18 or Edwards syndrome, with the exception of those who are stillborn.

The number, such as 13 or 18, refers to which chromosome the extra material comes from.


Achondrogenesis is a rare inherited disorder in which your child’s pituitary gland doesn’t make enough growth hormone. This causes severe bone problems, including a small lower jaw and a narrow chest. It also causes very short:

  • legs
  • arms
  • neck
  • torso


Progeria is a genetic condition that causes youra child to age at a rapid rate. Babies with progeria typically don’t show signs when they’re born, but they start showing signs of the disorder within the first 2 years of their life.

It’s due to a genetic mutation, but it’s not passed down through families. In addition to a small jaw, children with progeria may also have a slow growth rate, hair loss, and a very narrow face.

Cri-du-chat syndrome

Cri-du-chat syndrome is a rare genetic condition that causes developmental disabilities and physical deformities, including a small jaw and low-set ears.

The name derives from the high-pitched, cat-like cry that babies with this condition make. It’s usually not an inherited condition.

Treacher Collins syndrome

Treacher Collins syndrome is a hereditary condition that causes severe facial abnormalities. In addition to a small jaw, it can also cause a cleft palate, absent cheekbones, and malformed ears.

Call your child’s doctor if your child’s jaw looks very small or if your baby is having trouble eating or feeding. Some of the genetic conditions that cause a small lower jaw are serious and need a diagnosis as soon as possible so that treatment can begin.

Some cases of micrognathia may be diagnosed before birth with ultrasound.

Let your child’s doctor or dentist know if your child has trouble chewing, biting, or talking. Problems like these can be a sign of misaligned teeth, which an orthodontist or oral surgeon may be able to treat.

You may also notice that your child has trouble sleeping or has pauses in breathing during sleep, which may be due to obstructive sleep apnea from a smaller jaw.

Your child’s lower jaw may grow long enough on its own, especially during puberty. In this case, no treatment is necessary.

In general, treatments for micrognathia include modified eating methods and special equipment if your child is having trouble eating. Your doctor can help you find a local hospital that offers classes on this subject.

Your child may need corrective surgery performed by an oral surgeon. The surgeon will add or move pieces of bone to extend your child’s lower jaw.

Corrective devices, such as orthodontic braces, to fix misaligned teeth caused by having a short jaw can also be helpful.

Specific treatments for your child’s underlying condition depend on what the condition is, which symptoms it’s causing, and how severe it is. Treatment methods can range from medications and close monitoring to major surgery and supportive care.

If your child’s jaw grows longer on its own, feeding problems usually stop.

Corrective surgery is generally successful, but it can take 6 to 12 months for your child’s jaw to heal.

Ultimately, the outlook depends on the condition that caused micrognathia. Babies with certain conditions, such as achondrogenesis or trisomy 13, only live for a short time.

Children with conditions such as Pierre Robin syndrome or Treacher Collins syndrome can live relatively normal lives with or without treatment.

Your child’s doctor can tell you what the outlook is based on your child’s specific condition. Early diagnosis and ongoing monitoring help doctors determine if medical or surgical intervention is needed to ensure the best outcome for your child.

There’s no direct way to prevent micrognathia, and many of the underlying conditions that cause it can’t be prevented. If you have an inherited disorder, a genetic counselor can tell you how likely you are to pass it on to your child.