What is spina bifida primarily characterized by in a developing baby?

Spina bifida is primarily characterized by a defect in the development of the spinal cord and surrounding structures in a developing baby. This neural tube defect occurs when the spinal column does not close completely, which may lead to varying degrees of disability depending on the severity and location of the defect. The incomplete closure can result in damage to the spinal cord and nerves, leading to a range of physical and cognitive difficulties, including mobility issues, loss of sensation, and other related complications.

The other options, while they relate to various health conditions, do not accurately describe spina bifida. Vision issues, muscle tone reductions, and heart health conditions are not the primary characteristics associated with spina bifida; instead, the focus is firmly on the implications related to spinal cord development and the potential neurological impacts stemming from the defect.