Some women become very emotional, some are just nauseous all the time, some are just unpredictable all due to hormones. So for lack of a better terrm try to stay one step ahead rather than one step behind. Hopefully you know your wife well enough to know whether she wants attention or not. Some women need the hovering and some women DON”T want it. If she is a neat freak, be extra careful to stay in line and not make extra work for her, or better yet try to be vigilant and help clean so she won’t have to. If she gets sick from the smell of cooking, offer to help in the kitchen, get take out, ask your mother to cook and pick it up, do whatever it takes to address the issue.
Are you catching on yet? Don’t invite company over before checking with her and ask her “are you up for company?” don’t ask her “I really would like to have so and so over” that will make her feel guilty and she will do it for you whether she feels up to it or not. If you have other kids, help, help, help with them or get help for her especially with cleaning and laundry (lifting and bending is more difficult at this stage). Understand that it is more important for her to rest than for you to rest, so when Shabbos roles around be considerate of that and let her get a refreshing nap while YOU watch the other kids.
Always tell her how beautiful she looks, no matter how big she is getting, or how many pimples broke out on her face because she is going to be very critical about herself and her swollen ankles. And yes, remind her to put her feet up.
The more consideration you show her at this time in your marriage the more she will appreciate and respect you. S1, very nice of you to try and teach the young men these Shalom Bayis basics.