work issues

emg2010

This is my first pregnancy and I'm only about 5 maybe 6 weeks along. I know people wouldn't typically tell their employers until after 12 weeks but I'm considering telling work early. The reason I'm thinking of saying something early is because I work in an engineering/construction field. I work in an office but there are times that I'm sent to job sites and I work with equipment. My concern is being sent to this sites now and having to carry around heavy equipment.

 I'm not sure if I should mention something to my boss or wait?