There are several factors to consider before opening a UTMA account for your child. First, all transfers are irrevocable (which many people aren't aware of). Once you move assets into it, those belong to the UTMA's beneficiary.
Second, you cannot dictate how the beneficiary can use the assets once they gain ownership. For example, you may have intended the UTMA to help with educational expenses, but they choose instead to buy a car. Last, having a UTMA may lower your child's chances of securing financial aid because it'll show that they have resources (possibly enough that assistance is deemed unnecessary).