Working on HL

Is it an obligation to reply work email when on hospitalisation leave? And what's more, my boss texted me to reply email even though on HL, and asked me to lead a meeting. Can this be escalated some where? Looking at the screen for too long makes me nauseous and lightheadedness and it does not make me feel better at all. I'm 11 weeks pregnant now. #pleasehelp #advicepls