Whilst studying will be harder after you've had children, fertility does decrease from about your age onwards. You won't run out of eggs, but the chances of getting pregnant will decrease as you get older (having eggs doesn't necessarily mean you're fertile). The chances of birth defects and pregnancy complications also increase with increasing age. 33 is still young in age, but not really fertility wise.
Don't get me wrong, I am certainly NOT saying that you'll have any problems, but just be aware of your body and its capabilities.
As far as weighing up career vs. children, follow your heart. I chose to have my family while I can (because of endometriosis I would have struggled had I waited longer - I'm 28 and have just had my 1st) instead of chasing a career in medicine. Now I see how hard my friends have to study, and those who are already doctors have no life for themselves. Being a mum . . . I'm the one smiling =)
I'm a medical scientist