On the off chance that your insurance policy is an High Deductible Health Plan (HDHP) and you already have a Health Savings Account (HSA), let me note that instead of deducting medical mileage on Schedule A, that you can reimburse yourself for the medical mileage instead.
Let's say that you have 300 miles related to medical mileage. The normal medical mileage deduction in 2018 is 18 cents a mile. This would create a possible deduction of $54.00 (but read all the caveats by xmasbaby0 above).
Instead of adding this to the Medical and Dental Expenses section on Schedule A (where, as xmasbaby0 noted, you may get no deduction at all), you can instead choose to call your HSA administrator and ask that you be reimbursed from your HSA for that $300. The requirements are that your HSA already existed before you made the first drive to the NICU and that you have the cash in your HSA. Of course, if you don't have the cash in the HSA yet, you can delay the reimbursement until you do.
Since you have to put money in the HSA in order to be able to draw it out, you might wonder what the benefit to you would be. The benefit is that you get a tax deduction when you contribute that $300, so it actually costs you less than $300. If you are in the 12% tax bracket, then you are in essence getting a 12% discount on the 18 cents a mile that you spent on gas and wear-and-tear on your car.
In addition, if your employer is contributing to your HSA (many do), then your employer is, in effect, subsidizing your medical mileage with no tax consequence to you.
Which is better, taking the mileage on Schedule A or from your HSA? The tax benefit is the same but ONLY is you are able to use it on Schedule A. Many taxpayers cannot, as xmasbaby0 shows above. But you can always take the tax benefit from your HSA, so the answer would in most cases be "the HSA".
