After the hiring process is complete and a nanny has been selected, consider having her start before you go back to work. Doing so can really help you feel at ease, and can also help ease the transition for the baby.
Once you're back at work, you may want to stop by at home unannounced a few times in the first few weeks to see what is really going on. She will almost certainly be greeted by a happy nanny and baby, but she can also catch any problems before they get worse. For a more concerned mother, a nanny camera can be installed in the home (without telling the nanny) to record any misbehavior.
Above all, it is important for the new mom to try to relax. This can be difficult, but the truth is that a relaxed mom will make both the children and the nanny feel relaxed, which can ensure a pleasant relationship between everyone. A great nanny can become a loving member of your extended family.