Yeah, as the others said, you can set all the MCCC things you don't want to zero to turn them off.
Honestly tho, it's always baffled me that the game itself doesn't--or at least, doesn't even give the option to--adjust pregnancy lengths in proportion to the different lifespans. Whether on short, normal, or long, pregnancy always lasts 3 days, which is, as you pointed out, rather long for short lifespans, but also rather weirdly short for long lifespans as well. On "normal", pregnancy lasts about as long as the "baby" lifestage, but on long the "baby" lifestage is, like, 12 days! Which means that, conceivably (heh), a sim could get pregnant and give birth to 3 more babies before the first one even ages up to a toddler! (yes of course you could just age them up prematurely, but that's not really the point, some people (like me) don't like doing that generally and prefer to have the age spans more consistent).