Everything I've ever read/heard says to not push potty training before age 2. Some kids will show interest on their own earlier than that & it's fine to go w/ their interest, but pushing it too soon can actually backfire big time. My girls are 25 months old now & for quite awhile now they will randomly tell me that they need to poop or have pooped, they will randomly want to sit on the potty, but it's nowhere near all the time. I've known many people who have tried to potty train when the parent wants to & ends up taking forever with lots of set-backs. And I've known many people who've let each child take the lead & potty training has been a couple days & almost accident free. I'm planning to try some nakey time this summer since my kids are showing random interest & see if that's the push they need, but they're over 2.
Also keep in mind that even if you get them potty trained before the baby gets here, they may regress once the baby comes as a bid for attention.