Swim Instructor and Pregnant?!!

Do you think it's safe to continue being a swim instructor for kids ages 6 months-8 years when being pregnant? If so, up until what point in pregnancy would you stop?

Thanks!!!

Update: I told my Dr that there are occasions when I accidently do get hit or kicked in my stomach area and she insisted I stop immediately at 8 weeks. I felt that was a bit too extreme.