North American Registry of Midwives (NARM) Practice Exam

By what age is the posterior fontanel usually closed?

1. At birth

2. By 4 months

3. By 6 months

4. By 12 months

The correct answer is: By 4 months

The posterior fontanel, which is located at the back of a newborn's head, usually closes by approximately 4 months of age. This is a key developmental milestone as the closure of the posterior fontanel indicates that the bones of the skull are beginning to fuse appropriately, allowing for brain growth while maintaining some flexibility during birth. By this age, the rapid growth of the brain starts to stabilize, and the fontanel decreases in size, eventually resulting in its closure. While the other options indicate various ages for closure, they do not align with the commonly accepted developmental timeline. For instance, the closure at birth would not allow for the necessary growth and expansion of the brain, while closure by 6 or 12 months would suggest a delay in this normal development and could cause concern regarding cranial growth patterns.