Final answer:
The normal reduction in the number of fetal brain neurons during gestation is related to the maturation of the nervous system, akin to the 'pruning' process that occurs postnatally, although a specific term for this fetal phase was not provided.
Step-by-step explanation:
The normal loss of 25-40% of neurons in the fetal brain during the second half of gestation does not have a specific term provided in the provided materials. However, this process is related to the normal development of the nervous system, where there is a reduction in the number of neurons as the brain becomes more efficient. It is part of the natural developmental process and is necessary for the proper maturation of the brain. The term that most closely aligns with this process, based on the available context, would be 'pruning', even though it typically refers to the loss of neurons and neural connections later in development, specifically postnatal brain development during childhood and adolescence.