my son is 2 and im 17 weeks preg -
my gp told me not to lift mY son but that is just impossible and it really is useless advice!
i've just stuck with lifting him when i need to and try not to worry about it at all - just lift properly so you dont strain any muscles in the process. I've had to stop carrying him (mostly) unless it is 100% necessary.
Ive taught him to climb in and out of the car seat by himself so i only have to strap him in, moved him in to a toddler bed, so no more lifting in and out of cot, and I change his nappy on the floor.

speaking of being pregnant with toddlers - are you guys ExHaUsTeD!? I am! apart from the first few hours in the morning, im physically wrecked and just want to put my feet up and I have to have a nap when my son does (thankfully he still does nap!)