It shouldn't change if you do it right.
A graduate fellowship is not self-employment income, you are a student in training, not a business person trying to make a profit. If you entered the income as "other uncommon income" and answered the testing questions correctly, it would show up as "other income" and you would not be charged self employment tax.
However, the correct way to enter the income is to use the Education expense interview on the deductions and credits page. After entering the 1098-T (this should not be taxable, if the stipend just equals your tuition), keep going, and there should be additional questions about scholarships and fellowships. Your stipend is not subject to social security or medicare tax or self-employment tax but it is subject to regular income tax.
Also worth noting, that because this is not income earned from working, it is not "earned income" and does not qualify you for EIC, or certain other tax provisions that require earned income. Reporting it incorrectly as self-employment income might make you appear eligible for those credits. So entering the income the wrong way could create a swing in either the plus or minus direction, depending on SE tax vs. credits. But the correct answer is to enter it as a taxable scholarship or fellowship that is more than your qualified tuition expenses.
