Perhaps you might want to discuss with your gynae if this is possible. However, alternatively to inform your superior pertaining this issue which to me is unreasonable for preggy mum to be home late at third trimester and having to demand a lot. Alternatively, to the least offer WFH or office hours. This is very much unfair. To my opinion, I will be firm with my decision in raising my concern for the benefit of myself and baby. They like it or not, but they have to remember whether or not someone is pregnant, they are to be reasonable esp pertaining work issue.
Yes you can ask. Just let your gynae know that you’ve been feeling more exhausted due to work stress. If you go on in this way, it’ll be a matter of time that you’ll develop some troubling symptoms eg headache, body aches. Pretty sure you’re supposed to rest and focus on labour by 36 weeks onwards so gynae will be understanding of this.