Growing Up Healthy: Musculoskeletal Milestones in Baby’s First Year

One of the primary concerns for parents with a newborn is ensuring that the baby grows and develops normally. This is extremely important, since growth in the first year has a significant impact on the overall health and well-being of a child in later years. For parents, this means paying attention to musculoskeletal milestones in addition to weight and length.

According to the Mayo Clinic’s Infant and Toddler Health Center, “From birth to age 6 months, a baby may grow 1/2 to 1 inch (about 1.5 to 2.5 centimeters) a month and gain 5 to 7 ounces (about 140 to 200 grams) a week. Expect your baby to double his or her birth weight by about age 5 months.

From ages 6 to 12 months, a baby may grow 3/8 inch (about 1 centimeter) a month and gain 3 to 5 ounces (about 85 to 140 grams) a week. Expect your baby to triple his or her birth weight by about age 1 year.”

The musculoskeletal system represents the physical foundation for the baby’s growth and development. Most adults have 206 bones, but babies begin life with around 300 bones and cartilage elements, which fuse together as the baby develops. A baby’s cranium actually originates as several separate pieces, which allows the baby’s head to change shape as the bones slide over each other. Called molding, this process allows a baby to pass through the narrow birth canal to be born.

Known as the anterior and posterior (i.e., front and back) fontanelles, the two soft spots on the baby’s head are the gaps between the plates. According to the National Institutes of Health, “The fontanelle in the back of the head (posterior fontanelle) usually closes by the time an infant is 1 to 2 months old. The fontanelle at the top of the head (anterior fontanelle) usually closes between 7 to 19 months.”

A baby’s bones begin as cartilage, developing in the womb. After birth, the baby has some bones, but many are still cartilage at that point. As the baby grows, a process called ossification occurs, which hardens the cartilage into bone, which is joined by a nutrient artery to help it develop further. At six weeks, bone starts to develop as tightly wound chains of collagen, a protein. The minerals in the blood, along with the protein structure, start solidifying into the astonishingly resilient living material that is bone. The intricate joint mechanisms that lend the skeleton its elasticity and range of motion continue to mature long after birth.

For most parents, there are five musculoskeletal milestones that are particularly exciting, and it’s common for healthcare professionals who work with infants to ask about them:

• Lifting and supporting his or her head (sometimes called “head control”). Most infants can lift their heads slightly when they’re about a month old and hold it up when they’re placed in a sitting position at around four months. By 6 months, head control is usually steady.
• Rolling over. Some babies might be able to flip from belly to back around the 4-month mark, but most are able to master this maneuver at about 5 or 6 months. The back-top-front flip usually takes longer, though, because more neck and arm strength is needed.
• Remaining upright in a sitting position. Babies achieve this milestone at anywhere from 4 to 7 months. Most can sit well for several minutes without help by the time they’re 8 months old.
• Crawling. This typically happens sometime between the ages of 7 and 10 months. Some babies will also use other approaches to start getting mobile—bottom-sliding, belly-crawling and rolling are all common!
• Walking. First steps usually happen between 9 and 12 months and many babies are walking well by 14 or 15 months. However, it’s not unusual for a baby to start walking when they’re 16 of 17 months old.

As you’re watching for these milestones, it’s important to keep in mind that babies develop at different rates. In order for these processes to occur, proper nutrition and—yes—physical activity is essential. According to the American Academy of Orthopaedic Surgeons, “A healthy musculoskeletal system—consisting of bones, joints, ligaments, tendons and muscles—is essential to a child’s growth and development. Decisions made regarding children’s diet and levels of physical activity will not only affect them now, but also as they grow into adults.”

Chiropractic physicians are experts in diagnosing and treating musculoskeletal problems in patients of all ages. If you have questions or concerns about your child’s musculoskeletal development, please call or visit our office.