Chest Bone Development in Children

A child's chest bone, as well as surrounding bones, begins forming almost immediately after conception. In most cases, nature takes its course and a baby's chest bone forms normally on its own. In a small number of cases, something goes wrong, and the chest bone doesn't form the way it's supposed to, and that can cause certain chest deformities.

Prenatal Chest Bone Development

A baby's bones begin developing three weeks after conception, according to the Encyclopedia of Children's Health website 1. By the seventh week after conception, all 206 of a baby's bones are formed, though they are still quite soft and won't fully harden until after birth. In certain instances, the bones of the chest don't form the way they're supposed to, though there isn't usually a specific cause that doctors can pinpoint. According to a 2002 article published in the radiology journal "RadioGraphics," abnormal development can occur if an incorrect number of bones form, if the bones are the wrong shape or size or if the bones aren't properly mineralized, but it usually isn't possible to determine exactly why these things happen.

Chest Bone Development After Birth

After a baby is born, his bones continue to harden, which is a process called ossification. The bones in the chest are referred to as flat bones, according to the Encyclopedia of Children's Health website 1. These flat bones harden through a specific process called intramembranous ossification, which occurs when connective tissue forms around the bones. As this happens, the chest bones become stronger and harder. When the bones go through further growth, it's possible for an abnormality to occur, which can lead to certain chest bone conditions.

Potential Problems

There are two primary conditions that can occur when the chest bones don't develop properly. Pectus carinatum, or pigeon chest, occurs when the sternum and ribs stick out from the chest, causing it to bow out, according to Seattle Children's Hospital. The condition develops when there's a defect in the cartilage holding the ribs to the sternum. Pectus excavatum, or funnel chest, occurs when the breastbone sinks back into the chest 3. The causes of pectus excavatum aren't known, but it can run in families, according to 3.


Improper chest development can cause other health problems, according to the Boston Children's Hospital 1. Children with pectus carinatum often wear a brace designed to press the bones back where they're supposed to be. A doctor might recommend a brace because the condition can make it more difficult for a child to play and exercise normally, and it might also cause tenderness and pain in the chest area. Pectus excavatum can make it more difficult for a child to breathe normally when being active and can increase the chances of developing respiratory illnesses such as pneumonia 3. Pectus excavatum can also impact the function of the heart and lungs, according to 3. In instances of a severe deformity from either condition, surgery is often required to correct the shape of the chest wall. Prognosis after surgery is excellent for the vast majority of children, the Boston Children's Hospital notes.