Sticking to your regular exercise routine and controlling portion size over the holidays will allow you to keep a semblance of normality so that your energy levels are up and you can hit the ground running when you need to go back into work mode.
I support mothers by educating them on the physiological process of childbirth (in a fun way J), and then supporting them with exercises and practices that will shift the body back into the rest and digest mode post-delivery.