when to tell employer in relation to continued genetic tests

Hi! I'm 12 weeks and am showing, fatigued. I've got three tests coming up for genetic and abnormalities (I'm 40; first baby so a little stressed). Any thoughts on when to tell employer? My best face to face chance is my monthly review this Wednesday. In sales so they definitely need coverage for last two months (due date Nov 1). Suggestions are so appreciated!!!!!!