Reasons for Lack of Muscle Development in a Newborn

Although you wouldn’t expect a newborn to raise his head steadily and sit up straight from the get-go, you don’t want him to be completely floppy or unresponsive either. There are several disorders, situations and conditions that may contribute to lower than normal muscle development.

Normal Muscle Development

It’s normal for newborn babies to seem a bit floppy, since their muscles are still developing. While a baby is growing in the womb and running out of extra space, she doesn’t have the chance to work her muscles out to develop them; as she grows and matures in the outside world, her muscles will develop more tone and coordination. On the other hand, extreme floppiness or looseness should be addressed immediately with a pediatrician.


If a baby is born preterm, he may not have had enough time “in the oven” to develop properly and may suffer from poor muscle tone, among other possible issues. Often this poor muscle development is temporary and due to immaturity of the central nervous system. As his system matures, the condition usually improves.

Congenital Abnormalities

Certain congenital disorders can cause poor muscle tone and floppiness in a newborn. Children’s Hospital of Orange County and The University of Chicago state that Down syndrome, Prader-Willi syndrome and other chromosomal abnormalities can lead to muscle development problems 12. Spina bifida, hypothyroidism, congestive heart failure, storage disorders, hypoglycemia and other disorders can do this, too. Some of these issues can cause permanent muscle issues, while some are only temporary or can be resolved with physical therapy or surgery.


If there is trauma during the birth, it may cause nerve damage, spine injury or intracranial hemorrhage, leading to poor muscle development or lower body movement. Cerebral palsy is one of these conditions. If a baby is born breech or there was cervical cord trauma, there is also a risk of trauma.

Illness and Drugs

If the infant or pregnant mother contracts an illness or is exposed to certain medications, it may affect the baby’s muscle development. Herpes, toxoplasmosis, rubella and sepsis can contribute to this. If the mother was given the anti-seizure medication magnesium sulfate, benzodiazepine or spinal anesthesia, it can cause this condition. In addition, if a baby develops rickets or kernicterus, muscle development can be affected.