When my H went back to work I also felt overwhelmed. I somehow managed the physical, laborious side of it all but needed to know he was with me emotionally. It's knowing you're in this together and she can depend on you for support.
Things like asking about her AND the baby. Making sure she has all she needs for the day before you leave for work, offering to do some chores when you get home. Aknowledgement and reassurance that everything is going well. Empathising.
Ask her what would make her feel secure right now? Tell her you're prepared to do whatever it takes to make sure she feels safe.
Appreciate her for bringing a beautiful DS into your lives and how they mean the world to you :)
And lastly (unless she's one of the lucky one's who gets back to shape quickly) let her know you still find her attractive and beautiful as right now she's probably not feeling her prettiest.
Hope that helps!