I am going to water aerobics 3 times a week (I am 19 weeks) and really wasnt doing much prior to pregnancy other than walking.

there has been three different instructors. 2 of them and my doctor told me avoid the sit up type exercises. and when doing jumps dont bounce to much (like do the non impact level) and seperate legs slightly so your not coming up hard against your stomach.

the instructors mid class will tell me not to do something and wait and they give me something else. and of course stop for a minute if you feel uncomfortable and drink lots of water.

I am no expert but this is whats happened for me.

did you let the instructor know???