Some doctors recommend switching to non-underwired bras during pregnancy. Although it hasn’t been proven that underwires could be harmful, they may restrict the natural changes that your breasts go through, and interfere with your developing milk ducts.
If fitted properly, underwired bras are fine in the first stages of pregnancy but near the end it’s best to switch to a non-underwired one. There are plenty of good options around that will give you all the support you need.