Dogs babies and apartments

Question, so I live on the 2nd floor of an apartment. I have a almost 9 month old baby. I also have a dog. Who is 120lbs. How do you guys do potty breaks? Do you just lock the baby in the apartment and take the dog potty? My dog pulls so there would be no way to take him and the baby at the same time. It is way to risky going down the stairs as it is.