A: Although it is really hard to have a miscarriage or two, in your case, lifting heavy things won't cause a miscarriage. Miscarriages typically happen because the chromosomes in the fetus don't line up properly. That being said, doctors don't recommend that pregnant women lift heavy objects (more than 20 to 30 lbs.) for their own safety. Lifting heavy things can strain or really injure your back during pregnancy. If you are feeling dizzy, which is really common in the first trimester, this puts you at additional risk for falls. The timing for a leave of absence varies from patient to patient, based on their particular symptoms and their jobs. If possible, ask your employer to alter your work tasks, perhaps one with a sitting position or one that requires less lifting, and having a note from your doctor would be helpful.