Last name dilemma

I am 34yo, and when I divorced 5 years ago I decided to keep my ex’s last name so I would have the same last name as my son. I always thought I’d meet someone and remarry before having another baby, but unfortunately that hasn’t happened. Worried about the health complications and the possibility I may not remarry, I made a choice to go with a sperm donor and pursue the Single Mother By Choice route. Thankfully it worked! And even though I’m so excited, now I have to wonder- do I go through the process of going back to my maiden name and using that for the new baby, or is it weird if I use my married name so baby has the same last name as their brother?