Any time I've seen the midwives it has been a blood pressure check, listen to the baby's heartbeat and check a urine sample. So fill a jar with wee before you go in to them, they seem to expect you to know this in advance. You get the jar at the check in desk - they're up high beside the window. You'll also get a chance to ask any questions.
The consultant's appointment will be similar - you'll see the midwife again for wee and blood pressure and then the consultant will do a little scan.