I am a new tenure-track assistant professor who is expecting a baby in January (just after spring semester starts). I will be arriving on campus in the next couple of weeks and need to tell my department chair I am pregnant quite soon, as the teaching assignments for spring classes will be made shortly. 

I am assuming that I will not get any leave and I will need to teach my spring class, either in person or online. This is because I am in the US, and FMLA (Family and Medical Leave Act) protections don't apply until one has been employed for a year and the university doesn't offer anything beyond what is required by FMLA. 

My current strategy is to shoot the chair an email mentioning that I am on campus now and that I hope we can meet before the semester starts. During the meeting I plan to be straightforward and tell her I am expecting. I will tell her I am hoping to stop my tenure clock for a year and ask her to strategize with me on how to meet my teaching obligation in the spring, given that I will be due around the second week of classes.

What are the most important considerations when having this type of conversation with my chair? My main concern is my reputation in the department. I don't want to make a bad first impression, and I worry that some people might perceive this  unexpected turn of events negatively.