@DizzyDizzyDiana Yes, pregnant Sims don't age. They also can't die, but the main reason I think is that they don't want the mother to age out of being a valid age to have a baby (or worse, die of old age!).
And @mdpq47ozynb7 the high chairs are just ridiculously frustrating and buggy! I've stopped using them, FWIW. I put a plate on a kitchen counter or table and ask the toddler to grab a serving.
As for the parents caring for the toddler (or not), yes, alas, your Sim parents, especially if they're on different floors (or there are a lot of platforms in the house) have a tendency to drop their queues, or get distracted (especially by objects like basketball hoops, yoga mats, dancing...). It's like "feed the toddler, sure, let me go grab... SQUIRREL!!!!!" As others have suggested, it's probably an autonomy/AI problem. I love playing with autonomy on, but also they can frustrate you that way. Alas.
Toddlers are frustrating in the game, but if you get all their skills up you get some of the best bonuses in the game, so....