It does get easier. DD's just over two now and I can do more things while she plays.
While this isn't strictly about academic stimulation per se, I've taken on a philoophy of upskilling and making concrete efforts to become the kind of person I want to be in 10 years' time. It's easy for me to pine away thinking "Woe is me, I could be writing a bestselling children's book, but here I am folding washing" - and then go online and futz around for hours. Which is a rather wasteful use of my twenties, innit.
So I'm trying to actually be productive. I'm learning to knit and crochet; I've started fermenting veggies; I've even started using the dreaded spreadsheets to help organise my freelance writing. I've made myself a list (taped to the keyboard!) of all the writing/editing I have to do each day before I'm allowed to surf the web - including 15 minutes of fiction writing. (No, it isn't much, but rather than getting jealous of the single guys on writing forums who say they write for 3 hours a day I just figure it's better than nothing!) I've started getting out books from the library, and if I don't finish them all by the time I have to return them, well, too bad.
For you, with a 16-MO daughter, you'll probably have to work in shorter snippets. But you can still grab intellectual stimulation while you can! Are you partnered? Tell your SO that you need 20 minutes a day to write. Or type/surf the web while breastfeeding. Tape a crossword to the wall in the toilet and do a few clues every time you're in there - or tape a poem up and learn it. (Or anything, really - a passage from your religious text of choice, the Hobbit runes, the Greek alphabet, a list of French nouns, the table of elements, a map of the world, a list of words you can never remember how to spell, a couple of syllogistic forms, a piece of music you're trying to learn, the lyrics to "We Didn't Start the Fire" - whatever!) Read aloud to your DD if she likes it - my dad used to read theological commentaries to my older sister when she was a baby.
Right now we're planning to TTC in 9 months of so (yikes!), so I'm trying to get some "me" stuff in before that. I wanted to try my hand at drama, but it might be a bit late for that now - oh well, next time! I'm relishing the chance to do some moderately uninterrupted knitting, reading, writing etc. I don't know your philosophies on child spacing, but if you are comfortable with it I think it can help to have a vague plan. You can go "OK, I'll write next year off in terms of personal development, then have a gap of 3 years, start taking a paper at Uni when the baby turns two, learn to do X, Y and Z and save up for a holiday before TTC again"... or whatever. I'm still struggling with the whole thing myself, but when I get into a seasons-of-life, flowy, everything-has-its-time sort of mood it helps. For a while.